Which diagram correctly shows light traveling in a straight line?

Figure (a) showing light through a straight pipe

Figure (b) showing light through a bent pipe

A diagram of light scattering in all directions

A diagram of light curving around an obstacle

Why does a shadow form when an opaque object is placed in the path of light?

The object blocks the path of light.

The object emits its own light.

The object blocks the path of light.

The object reflects all the light.

What is the primary function of a periscope?

To see objects that are not directly visible.

To measure the intensity of light.

Which of the following activities best demonstrates that light travels in a straight line?

Observing a shadow formed by an object.

Seeing your reflection in a mirror.

Observing a shadow formed by an object.

Looking at colorful patterns in a kaleidoscope.

Seeing objects through frosted glass.

If you move an opaque object closer to the light source, keeping the screen fixed, what happens to its shadow?

The shadow's size remains the same.

Which of the following correctly describes the path of light in a simple periscope?

Light enters, reflects off two mirrors, then exits.

Light enters, reflects off one mirror, then exits directly.

Light enters, reflects off two mirrors, then exits.

Light bends through a curved tube without mirrors.

Light passes through a single lens to magnify the view.

What happens to the light spot on a screen if you move one of the matchboxes slightly in Activity 11.1 (light through holes)?

The light spot becomes brighter.

The light spot becomes dimmer but stays visible.

Assertion (A): The image formed by a plane mirror is always virtual and erect. Reason (R): Plane mirrors reflect light rays in such a way that they appear to originate from behind the mirror, but do not actually meet.

A and R both correct, R explains A

Which of the following statements about shadows are correct? Select all that apply.

Shadows are formed only when light travels in a straight line.

The color of the object affects the color of its shadow.

Shadows are always formed on the opposite side of the light source.

Shadows can be formed by transparent objects.

Assertion (A): A kaleidoscope produces an infinite number of patterns. Reason (R): It uses multiple reflections from three plane mirrors arranged at an angle to each other.

A and R both correct, R explains A

A student performs an experiment to study shadow formation. They use a torch, an opaque object, and a screen. Which of the following changes would result in a larger and less distinct shadow?

Moving the object closer to the torch.

Moving the object closer to the screen.

Moving the object closer to the torch.

Moving the torch closer to the screen.

Which of the following statements are true regarding the image formed by a plane mirror? Select all that apply.

It is formed at the same distance behind the mirror as the object is in front.

It can be obtained on a screen.

Assertion (A): The image of a tree seen through a pinhole camera is upside down. Reason (R): Light rays from the top of the tree pass through the pinhole and reach the bottom of the screen, and vice-versa, due to rectilinear propagation.

A and R both correct, R explains A

A student is trying to see a distant object through a self-made pinhole camera. What adjustments should they make to get a clear image on the tracing paper screen?

Move the screen farther from the pinhole.

Move the screen closer to the pinhole.

Move the screen farther from the pinhole.

Use an opaque screen instead of tracing paper.

Is this CBSE Class 7 Science Chapter 11 quiz free?

Yes, this quiz on 'Light: Shadows and Reflections' is completely free for all students. No registration or payment is required.

How many questions are in the game mode for this chapter?

The game mode for Chapter 11, 'Light: Shadows and Reflections', features a total of 40 unique questions across easy, medium, and hard difficulty levels.

Are the questions based on the NCERT textbook?

Absolutely! All questions are meticulously designed and grounded in the NCERT Class 7 Science textbook for Chapter 11, ensuring alignment with your curriculum.

Can I practice the NCERT textbook questions here?

Yes, our 'Book Questions' section provides solved versions of the NCERT textbook exercises for Chapter 11, helping you understand the correct approach to each problem.

What topics does this quiz cover?

This quiz covers all key topics from Chapter 11, including sources of light, light propagation, transparent/translucent/opaque materials, shadow formation, reflection, plane mirror images, and pinhole cameras.

What is a luminous object?

A luminous object is one that emits its own light, such as the Sun or a lit candle. This quiz will test your understanding of such concepts.

Home › CBSE › Class 7 › Science › Light: Shadows and Reflections

CBSE · Class 7 · 🔬 Science · Chapter 11

Light: Shadows and Reflections

Luminous and Non-Luminous ObjectsPropagation of LightTransparent, Translucent, and Opaque MaterialsShadow FormationReflection of LightImages Formed by Plane Mirrors

Chapter 11, 'Light: Shadows and Reflections', introduces students to fundamental properties of light. It explains sources of light, how light travels in straight lines, the formation of shadows by opaque objects, and the reflection of light by mirrors. Students learn about transparent, translucent, and opaque materials, and how images are formed in plane mirrors and pinhole cameras. The chapter also covers practical applications like periscopes and kaleidosc, making it crucial for understanding optics.

Luminous and Non-Luminous Objects

Light hamare aas-paas ki cheezein dekhne mein help karti hai. Light ke bina sab kuch dark hota.

Sources of Light: Wo cheezein jo light produce karti hain.
Natural Sources: Jo nature mein khud se light dete hain.
Examples: Sun, Stars, Firefly (jugnu), Lightning.
[IMAGE: natural_sources_of_light_fig111] mein natural sources dekho.
Artificial Sources: Jo insaano ne banaye hain light produce karne ke liye.
Examples: Candle, Oil lamp, Electric bulb, Tube light.
[IMAGE: artificial_sources_of_light_fire_fig112] aur [IMAGE: electric_light_sources_fig113] mein artificial sources dekho.

Luminous Objects:
Wo objects jo apni khud ki light emit karte hain.
Examples: Sun, Stars, Torch (jab on ho), Candle flame, Electric bulb.

Non-Luminous Objects:
Wo objects jo apni khud ki light emit nahi karte hain.
Ye objects light ko reflect karte hain jo unpar padti hai, isliye hum unhe dekh paate hain.
Examples: Moon, Earth, Table, Chair, Books, Human beings.
Moon ek non-luminous object hai. Ye Sun ki light ko reflect karke chamakta hai.

❗Important

Moon non-luminous hai. Ye Sun ki light ko reflect karta hai.

📖Definition

Luminous Objects: Objects jo apni khud ki light produce karte hain. Non-Luminous Objects: Objects jo apni khud ki light produce nahi karte hain, balki light ko reflect karte hain.

Light Travels in a Straight Line (Rectilinear Propagation of Light)

Light hamesha seedhi line mein travel karti hai. Is property ko Rectilinear Propagation of Light kehte hain.

Proof (Activities):
Activity 11.1 (Matchbox Experiment):
Teen matchboxes mein holes ko align karke light pass karne par, light spot dikhta hai.
Agar ek bhi matchbox move kar diya jaye, toh light spot gayab ho jata hai.
Ye show karta hai ki light ko pass hone ke liye ek straight path chahiye.
[IMAGE: light_travels_in_a_straight_line_experiment_fig114] dekho.
Activity 11.2 (Bent Pipe Experiment):
Ek straight pipe se candle flame dikhti hai.
Usi pipe ko bend karne par candle flame nahi dikhti.
Iska matlab light curved path follow nahi karti.
[IMAGE: light_travels_in_a_straight_line_fig115] dekho.

Importance:
Is property ki wajah se hi shadows bante hain aur pinhole camera kaam karta hai.
Light ki speed bahut zyada hoti hai (approximately \(3 \times 10^8\) meters per second in vacuum).

📖Definition

Rectilinear Propagation of Light: Light ka ek seedhi line mein travel karna.

⭐Remember

Light ki speed vacuum mein sabse zyada hoti hai. Ye hamesha straight path follow karti hai.

Transparent, Translucent, and Opaque Materials

Objects ko unki light pass karne ki ability ke according classify kiya jata hai:

Transparent Materials:
Ye materials light ko apne through poori tarah se pass hone dete hain.
Inke through hum objects ko clear dekh sakte hain.
Examples: Clean glass, Air, Pure water.

Translucent Materials:
Ye materials light ko partially pass hone dete hain.
Inke through objects clear nahi, balki blurry ya hazy dikhte hain.
Examples: Frosted glass, Oiled paper, Tracing paper, Thin cloth.

Opaque Materials:
Ye materials light ko apne through bilkul bhi pass nahi hone dete hain.
Inke through hum kuch bhi nahi dekh sakte hain.
Yehi materials shadows banate hain.
Examples: Wood, Cardboard, Metal, Wall.

[IMAGE: light_passing_through_different_materials_fig116] mein inka comparison dekho.

💡Tip

In teeno types ke materials ke definitions aur examples bahut important hain. Aksar exam mein pucha jata hai.

Formation of Shadows

Shadows tab bante hain jab light ke path mein koi opaque object aa jata hai.

Shadow Formation ke liye Essential Conditions:

Light Source: Light ka koi source hona chahiye (e.g., Sun, Torch).
Opaque Object: Ek opaque object hona chahiye jo light ko block kar sake.
Screen: Ek surface (screen) jahan shadow ban sake (e.g., Wall, Ground).

Shadows ki Properties:
Shadows hamesha dark hote hain, chahe object ka color kuch bhi ho.
Shadows object ki shape ko resemble karte hain, lekin uski exact copy nahi hote.
Shadows ka size aur shape light source, object aur screen ke relative positions par depend karta hai.
Agar object light source ke paas hai, toh shadow bada banta hai.
Agar object screen ke paas hai, toh shadow chhota banta hai.
Shadows hamesha light source ke opposite direction mein bante hain.
Transparent objects shadow nahi banate. Translucent objects faint shadows banate hain.

Activity 11.4 (Shadow Observation):
Different opaque objects ke shadows observe karne se pata chalta hai ki shadow ka size aur shape change ho sakta hai object ki position change karne par.
[IMAGE: shadows_around_us_fig117] mein shadows ke examples dekho.

📖Definition

Shadow: Ek dark patch jo tab banta hai jab koi opaque object light ke path ko block karta hai.

⭐Remember

Shadows ka color hamesha black ya dark grey hota hai, object ke color par depend nahi karta.

Reflection of Light

Jab light kisi shiny surface se takra kar wapas bounce karti hai, toh us phenomenon ko Reflection of Light kehte hain.

Reflecting Surfaces:
Highly polished aur smooth surfaces light ko achhe se reflect karte hain.
Examples: Plane mirror, Shiny metal surfaces, Still water surface.

Key Terms:
Incident Ray: Wo light ray jo surface par padti hai.
Reflected Ray: Wo light ray jo surface se bounce back hoti hai.
Point of Incidence: Wo point jahan incident ray surface se takrati hai.
Normal: Point of incidence par surface ke perpendicular (90 degree) draw ki gayi imaginary line.
Angle of Incidence (i): Incident ray aur normal ke beech ka angle.
Angle of Reflection (r): Reflected ray aur normal ke beech ka angle.

Laws of Reflection (Class 7 mein basic understanding):

Angle of incidence hamesha angle of reflection ke equal hota hai (\(i = r\)).
Incident ray, reflected ray, aur normal, teeno ek hi plane mein hote hain.

Activity 11.6 (Mirror and Comb Experiment):
Comb ke slit se aati light ray ko mirror par dalne par, light ki direction change ho jati hai.
Ye show karta hai ki mirror light ko reflect karta hai.
[IMAGE: reflection_of_light_fig119] mein setup dekho.

Uses of Reflection:
Mirror mein apna face dekhna.
Vehicles ke rear-view mirrors.
Periscopes aur kaleidoscopes mein.
[IMAGE: reflection_of_light_using_a_mirror_fig118] mein sunlight ko redirect karna dekho.

📖Definition

Reflection of Light: Light ka kisi surface se takra kar wapas usi medium mein bounce back hona.

❗Important

Plane mirrors light ko regular reflection karte hain, jisse clear images banti hain.

Images Formed by a Plane Mirror

Plane mirror ek flat, smooth reflecting surface hota hai. Isse banne wale images ki kuch specific properties hoti hain.

Properties of Image Formed by a Plane Mirror:

Virtual Image: Image mirror ke peeche banti hai aur use screen par obtain nahi kiya ja sakta. Ye sirf appear hoti hai ki light rays wahan se aa rahi hain.
Erect (Upright): Image seedhi hoti hai, object ki tarah.
Same Size: Image ka size object ke size ke barabar hota hai.
Same Distance: Image mirror ke peeche utni hi doori par banti hai jitni doori par object mirror ke saamne hota hai.
Laterally Inverted: Image side-wise ulta ho jata hai. Matlab, object ka left side image ka right side dikhta hai aur object ka right side image ka left side dikhta hai.

Example: Agar aap mirror mein apna right hand uthayenge, toh image ka left hand uthta hua dikhega.
AMBULANCE word ko ambulance par ulta likha jata hai taaki mirror mein seedha dikhe.

Activity 11.7 & 11.8:
Pen ko mirror ke saamne rakh kar uski image observe karna.
Apni image ko mirror mein dekh kar distance aur lateral inversion observe karna.
[IMAGE: image_formed_by_a_plane_mirror_fig1110] aur [IMAGE: observing_image_in_a_plane_mirror_fig1111] mein image formation dekho.

📖Definition

Virtual Image: Wo image jise screen par obtain nahi kiya ja sakta. Ye tab banti hai jab reflected rays appear to meet at a point.

📖Definition

Lateral Inversion: Image ka side-wise ulta ho jana (left appears right, right appears left).

💡Tip

Plane mirror se banne wali image ki paanch properties bahut important hain. Inhe yaad rakho!

Working of a Pinhole Camera

Pinhole camera ek simple device hai jo light ke rectilinear propagation principle par kaam karta hai.

Construction:
Ek dark box hota hai jiske ek side par bahut chhota hole (pinhole) hota hai.
Opposite side par ek translucent screen (jaise tracing paper) lagi hoti hai.
[IMAGE: pinhole_camera_fig1113] mein sliding pinhole camera ka construction dekho.

Working Principle:
Object se aane wali light rays seedhi line mein travel karti hain.
Ye rays pinhole se pass hokar screen par padti hain.
Upar se aane wali rays neeche jaati hain aur neeche se aane wali rays upar jaati hain.
Isse screen par inverted image banti hai.
[IMAGE: pinhole_camera_fig1112] mein candle flame ki inverted image dekho.

Characteristics of Image Formed by Pinhole Camera:

Real Image: Image ko screen par obtain kiya ja sakta hai.
Inverted: Image ultii (upside down) banti hai.
Smaller/Larger: Image ka size object ke size se chhota ya bada ho sakta hai, object ki distance aur pinhole se screen ki distance par depend karta hai.
Coloured: Image object ke color ki hoti hai.

Factors Affecting Image:
Pinhole Size: Agar pinhole bahut bada hoga, toh image blurry ya multiple images banegi. Agar bahut chhota hoga, toh image faint banegi.
Distance: Object aur screen ki distance change karne se image ka size change hota hai.

❗Important

Pinhole camera light ke rectilinear propagation ke principle par based hai.

📖Definition

Real Image: Wo image jise screen par obtain kiya ja sakta hai. Pinhole camera real image banata hai.

Applications of Light Principles: Periscope and Kaleidoscope

Light ke reflection aur rectilinear propagation ke principles ka use karke kai useful devices banaye jaate hain.

Periscope

Principle: Multiple reflections of light.
Construction:
Ek Z-shaped tube hota hai.
Isme do plane mirrors 45 degree ke angle par ek dusre ke parallel fit kiye hote hain.
[IMAGE: periscope_fig1114] mein periscope ka diagram dekho.
Working:
Object se light rays upper mirror par padti hain.
Upper mirror se reflect hokar light rays tube ke andar neeche aati hain.
Neeche wale mirror se reflect hokar light rays observer ki aankh tak pahunchti hain.
Isse hum aise objects dekh paate hain jo direct line of sight mein nahi hote.
Uses:
Submarines mein surface ke upar dekhne ke liye.
Tanks mein bahar dekhne ke liye.
Soldiers bunkers se bahar ki situation dekhne ke liye.

Kaleidoscope

Principle: Multiple reflections of light.
Construction:
Teen rectangular plane mirror strips ko triangular shape mein join kiya jata hai.
Inhe ek circular tube mein rakha jata hai.
Ek end par transparent plastic sheet aur uske upar rang-birange toote hue bangles ya beads rakhe jaate hain.
Dusre end par tracing paper se cover kiya jata hai.
[IMAGE: kaleidoscope_fig1115] mein kaleidoscope ka construction dekho.
Working:
Jab tube ko ghumaya jata hai, toh andar rakhe hue objects ke multiple reflections mirrors mein bante hain.
Ye reflections ek dusre se interact karke beautiful aur symmetrical patterns banate hain.
Uses:
Entertainment ke liye.
Designers aur artists naye patterns ke ideas generate karne ke liye use karte hain.

⭐Remember

Periscope aur Kaleidoscope dono multiple reflections of light ke principle par kaam karte hain.

💡Tip

Periscope aur Kaleidoscope ke principles aur uses aksar short answer questions mein puche jaate hain.

Easy (15)

Which of the following is a luminous object?
- Moon
- Mirror
- Sun (correct)
- Book
Why: The Sun emits its own light, making it a luminous object.
Light travels in a ____________ line.
Why: Light always travels in a straight path.
Objects that do not emit their own light are called non-luminous objects.
Why: Non-luminous objects reflect light from other sources.
Which material allows light to pass through it almost completely?
- Opaque
- Translucent
- Transparent (correct)
- Reflective
Why: Transparent materials allow light to pass through them completely.
A dark patch formed when light is blocked by an opaque object is called a __________.
Why: Shadows are formed when opaque objects block light.
The image formed by a plane mirror is always inverted.
Why: Plane mirrors form erect images, not inverted.
Which of the following describes a material that allows some light to pass through, but scatters it, making objects appear blurry?
- Transparent
- Opaque
- Translucent (correct)
- Luminous
Why: Translucent materials allow partial and scattered light transmission.
The phenomenon where light changes its direction after striking a mirror is called __________.
Why: Reflection is the bouncing back of light from a surface.
A pinhole camera forms an image that is always upright.
Why: Pinhole cameras form inverted images.
Identify the object that is a natural source of light from the given options.
- Candle
- Electric bulb
- Sun (correct)
- Torch
Why: The Sun is a natural source of light, unlike artificial sources like candles or bulbs.
Which of the following is NOT a characteristic of the image formed by a plane mirror?
- Same size as the object
- Erect
- Can be obtained on a screen (correct)
- Laterally inverted
Why: Images formed by plane mirrors are virtual and cannot be projected onto a screen.
A periscope uses __________ to allow us to see objects not directly visible.
Why: Periscopes use two mirrors to reflect light and enable indirect viewing.
The Moon is a luminous object because it shines brightly in the night sky.
Why: The Moon is non-luminous; it reflects sunlight.
Which diagram correctly shows light traveling in a straight line?
- Figure (a) showing light through a straight pipe (correct)
- Figure (b) showing light through a bent pipe
- A diagram of light scattering in all directions
- A diagram of light curving around an obstacle
Why: Light travels in straight lines, as demonstrated by seeing through a straight pipe.
Opaque objects form darker shadows compared to translucent objects.
Why: Opaque objects block all light, creating dark shadows.

Medium (15)

Why does a shadow form when an opaque object is placed in the path of light?
- The object emits its own light.
- Light bends around the object.
- The object blocks the path of light. (correct)
- The object reflects all the light.
Why: Shadows form because opaque objects prevent light from passing through them.
Match the type of material with its light transmission property.
Why: Materials are classified by how much light they let through: transparent (all), translucent (some, scattered), opaque (none).
The image formed by a plane mirror is always of the __________ size as the object.
Why: Plane mirrors produce images that are the same size as the object.
Arrange the following steps for making a simple pinhole camera in the correct order:
Why: The steps involve preparing two boxes, making a pinhole, creating a screen, and assembling the camera.
What is the primary function of a periscope?
- To magnify distant objects.
- To produce colorful patterns.
- To see objects that are not directly visible. (correct)
- To measure the intensity of light.
Why: Periscopes use mirrors to allow viewing around obstacles.
Match the object with its classification regarding light.
Why: Objects are classified by how they interact with light: clear glass (transparent), wooden door (opaque), frosted glass (translucent), lit candle (luminous).
The image formed by a pinhole camera is always __________.
Why: Pinhole cameras produce images that are upside down.
Which of the following activities best demonstrates that light travels in a straight line?
- Seeing your reflection in a mirror.
- Observing a shadow formed by an object. (correct)
- Looking at colorful patterns in a kaleidoscope.
- Seeing objects through frosted glass.
Why: Shadow formation directly proves light's straight-line path.
Match the device with its primary function.
Why: Each device utilizes light properties for a specific purpose: pinhole camera (inverted image), plane mirror (reflection), periscope (indirect viewing), kaleidoscope (patterns).
What term describes the left-right reversal observed in an image formed by a plane mirror?
Why: Lateral inversion is the left-right reversal in plane mirror images.
If you move an opaque object closer to the light source, keeping the screen fixed, what happens to its shadow?
- The shadow becomes smaller.
- The shadow becomes larger. (correct)
- The shadow's size remains the same.
- The shadow disappears.
Why: Moving an object closer to the light source makes its shadow larger.
What is the term for an upright image?
Why: An erect image is one that is upright, not inverted.
Which of the following correctly describes the path of light in a simple periscope?
- Light enters, reflects off one mirror, then exits directly.
- Light enters, reflects off two mirrors, then exits. (correct)
- Light bends through a curved tube without mirrors.
- Light passes through a single lens to magnify the view.
Why: A periscope uses two mirrors for two reflections to redirect light.
What happens to the light spot on a screen if you move one of the matchboxes slightly in Activity 11.1 (light through holes)?
- The light spot becomes brighter.
- The light spot becomes dimmer but stays visible.
- The light spot disappears. (correct)
- The light spot changes color.
Why: Moving a matchbox breaks the straight path, causing the light spot to disappear.
Match the property of light with its corresponding phenomenon.
Why: Rectilinear propagation leads to shadows, reflection to mirror images, opaque objects block light, and translucent objects scatter it.

Hard (10)

Assertion (A): The image formed by a plane mirror is always virtual and erect. Reason (R): Plane mirrors reflect light rays in such a way that they appear to originate from behind the mirror, but do not actually meet.
Why: The virtual nature of the image is due to reflected rays appearing to diverge from behind the mirror.
A student is observing the image of a candle flame through a pinhole camera. The candle is placed 50 cm from the pinhole, and the screen is 10 cm behind the pinhole. If the candle flame is 5 cm tall, what will be the approximate height of the image on the screen?
- 1 cm (correct)
- 2 cm
- 5 cm
- 10 cm
Why: The image height is proportional to the screen distance divided by the object distance.
Which of the following statements about shadows are correct? Select all that apply.
- Shadows are formed only when light travels in a straight line. (correct)
- The color of the object affects the color of its shadow.
- Shadows are always formed on the opposite side of the light source. (correct)
- Shadows can be formed by transparent objects.
Why: Shadows result from light blocking and are always opposite the light source. Transparent objects don't form shadows.
Observe the image showing a periscope. What is the angle of incidence for the light ray on the first mirror if it enters horizontally and is reflected vertically downwards?
- 0 degrees
- 30 degrees
- 45 degrees (correct)
- 90 degrees
Why: For a 90-degree turn (horizontal to vertical), the mirror must be at 45 degrees, making the angle of incidence 45 degrees.
Assertion (A): A kaleidoscope produces an infinite number of patterns. Reason (R): It uses multiple reflections from three plane mirrors arranged at an angle to each other.
Why: Multiple reflections in a kaleidoscope create numerous unique patterns.
A student performs an experiment to study shadow formation. They use a torch, an opaque object, and a screen. Which of the following changes would result in a larger and less distinct shadow?
- Moving the object closer to the screen.
- Moving the object closer to the torch. (correct)
- Moving the torch closer to the screen.
- Using a smaller opaque object.
Why: Moving the object closer to the light source causes light to diverge more, creating a larger, less distinct shadow.
Which of the following statements are true regarding the image formed by a plane mirror? Select all that apply.
- It is always virtual. (correct)
- It is always inverted.
- It is formed at the same distance behind the mirror as the object is in front. (correct)
- It can be obtained on a screen.
Why: Plane mirror images are virtual, erect, laterally inverted, and equidistant from the mirror.
Assertion (A): The image of a tree seen through a pinhole camera is upside down. Reason (R): Light rays from the top of the tree pass through the pinhole and reach the bottom of the screen, and vice-versa, due to rectilinear propagation.
Why: The inverted image in a pinhole camera is a direct result of light traveling in straight lines.
Observe the setup in Fig. 11.9b. If the angle between the incident light beam and the mirror surface is 30 degrees, what is the angle between the incident ray and the reflected ray?
- 30 degrees
- 60 degrees
- 90 degrees
- 120 degrees (correct)
Why: The angle between incident and reflected ray is twice the angle of incidence. If the angle with the surface is 30 degrees, the angle of incidence is 60 degrees, so the total angle is 120 degrees.
A student is trying to see a distant object through a self-made pinhole camera. What adjustments should they make to get a clear image on the tracing paper screen?
- Make the pinhole larger.
- Move the screen closer to the pinhole.
- Move the screen farther from the pinhole. (correct)
- Use an opaque screen instead of tracing paper.
Why: Adjusting the screen distance (focussing) is necessary for a clear image in a pinhole camera.