NCERT Solutions for Chapter 10 Light Reflection and Refraction Class 10 Science

Last Updated : 17 Nov, 2023

NCERT Solutions for Class 10 Science Chapter 10 Light – Reflection and Refraction- This article includes free NCERT Solutions for Class 10 Science Chapter 10 Light – Reflection and Refraction, developed by the top Biology experts at GFG, according to the latest CBSE Syllabus 2023-24 and guidelines. The solutions to all the exercises in NCERT Class 10 Science Chapter 10 Light – Reflection and Refraction have been collectively covered in NCERT Solutions for Class 10.

Also, to learn the basic concepts of NCERT Class 10 Chapter 10 Light – Reflection and Refraction from scratch, check out Class 10 NCERT Science Chapter 10 Light – Reflection and Refraction.

NCERT Solutions for Class 10 Science Chapter 10 Light- Reflection and Refraction: Exercise

Q1. Which one of the following materials cannot be used to make a lens?(a) Water (b) Glass (c) Plastic (d) Clay

We cannot use clay to make lens because clay is an opaque material and light cannot pass through clay. Thus we cannot see anything through a clay lens.

Thus option (d) clay is the correct answer.

Q2. The image formed by a concave mirror is observed to be virtual, erect and larger than the object. Where should be the position of the object?(a) Between the principal focus and the centre of curvature(b) At the centre of curvature(c) Beyond the centre of curvature(d) Between the pole of the mirror and its principal focus.

Concave image forms a virtual, erect and larger image when the object is between the principal focus and pole of the mirror.

Thus option (d) is the correct answer.

Q3. Where should an object be placed in front of a convex lens to get a real image of the size of the object?(a) At the principal focus of the lens(b) At twice the focal length(c) At infinity(d) Between the optical centre of the lens and its principal focus.

To get a real image of the object through a convex lens, we need to place the object at a distance equal to radius of curvature of the lens which is twice the focal lengh.

Thus option (b) is the correct answer.

Q4. A spherical mirror and a thin spherical lens have a focal length of -15 cm. The mirror and the lens are likely to be(a) both concave(b) both convex(c) the mirror is concave, and the lens is convex(d) the mirror is convex, but the lens is concave

The focal length given here is negative. Negative focal length is a property of concave mirror. Thus the mirror and lens both are concave.

Thus option (a) is the correct answer.

Q5. No matter how far you stand from a mirror, your image appears erect. The mirror is likely to be (a) plane (b) concave (c) convex (d) either plane or convex.

A plane and convex mirror always form an erect image. Thus the mirror is likely to be either plane or convex.

Thus option (d) is the correct answer.

Q6. Which of the following lenses would you prefer to use while reading small letters found in a dictionary?(a) A convex lens of focal length 50 cm(b) A concave lens of focal length 50 cm(c) A convex lens of focal length 5 cm(d) A concave lens of focal length 5 cm

A mirror with shorter focal length has a higher magnification power and a convex lens makes an erect image when object is between the mirror and its focal length. Thus we will make use of a convex mirror with focal length of 5cm.

Thus option (c) is the correct answer.

Q7. We wish to obtain an erect image of an object, using a concave mirror of focal length 15 cm. What should be the range of distance of the object from the mirror? What is the nature of the image? Is the image larger or smaller than the object? Draw a ray diagram to show the image formation in this case.

A concave mirror will form an erect image of an object when the distance of object from the mirror is less than its focal length. Thus we will place the image between 0 to 15 cm. The image thus formed is virtual, erect, and enlarged (larger than the object). The ray diagram is shown below:

Q8. Name the type of mirror used in the following situations.(a) Headlights of a car(b) Side/rear-view mirror of a vehicle(c) Solar furnaceSupport your answer with a reason.

(a) A concave mirror is used in the headlights of car because when the light source is placed at the focus of the concave mirror, it produces a powerful parallel beam of light which helps to see the objects on the front of car clearly to a large distance.

(b) Side/ rear view mirror of a vehicle is a convex mirror because we need to see a large amount of area and vehicles behind us while driving. A convex mirror is used because a convex mirror forms a virtual and diminished image of the objects which provide us with a smaller view of the large area.

(c) Solar furnace makes use of concave mirror because the sun’s rays coming from infinity are converged by the concave mirror at its focus which concentrates the energy at a particular point to produce a high temperature.

Q9. One-half of a convex lens is covered with black paper. Will this lens produce a complete image of the object? Verify your answer experimentally. Explain your observations.

Yes, the lens will produce a complete image of the object but the image will be reduced in intensity. This is because to form an image, we need only two rays of light coming from an object. As the upper portion of lens is not covered, at least two rays can pass through upper part of lens and form the image. This can be verified by an experiment.

Experiment: To show that a half lens can produce a complete image of an object

Requirements: Convex lens, Candle, matchstick, Two black sheets of paper, Table

Procedure:

• Fix the convex lens on the table.
• Now light a candle with matchstick and place it on one side of the lens.
• Turn off the lights to ensure that the room is dark
• Take a sheet of paper and obtain the image of the candle on the sheet by moving it.
• Mark the positions of the candle, lens and image in this case.
• Now, cover one half of the lens with a black sheet.
• Repeat the above experiment.

Observations: A complete image of candle is obtained on the sheet but it is less bright as compared to previous image.

Thus, we conclude that a half lens can form a complete image of an object.

Q10. An object 5 cm in length is held 25 cm away from a converging lens of focal length 10 cm. Draw the ray diagram and find the position, size and nature of the image formed.

Given u = -25 cm, h = 5cm, f = 10 cm, h’ = ?

Using lens formula: 1/f = 1/v – 1/u

1/10 = 1/v – (-1/25)

1/v = 1/10 – 1/25

1/v = 15/250 = 3/50

v = 50/3 cm = 16.67 cm

We know that h/h’ = v/u

5/h’ = 50/3*(-25)

h’ = 250/(-75) = -10/3

h’ = 3.33 cm

Negative sign indicates that the image is inverted and diminished in size as h’ < h. It is formed at a distance of 16.67 cm behind the lens.

The ray diagram is shown below:

Q11. A concave lens of focal length 15 cm forms an image 10 cm from the lens. How far is the object placed from the lens? Draw the ray diagram.

Given u = ?, f = -15 cm, v = -10 cm

Using lens formula:

1/f = 1/v – 1/u

-1/15 = -1/10 – 1/u

1/u = -1/10 + 1/15

1/u = -5/150

u = -30 cm

Thus, the object is placed at a distance of 30 cm in front of the lens.

The ray diagram is shown below:

Q12. An object is placed at a distance of 10 cm from a convex mirror of focal length 15 cm. Find the position and nature of the image.

Given u = -10 cm, f = 15 cm

Using mirror formula : 1/f = 1/v + 1/u

1/15 = 1/v + (-1/10)

1/v = 1/15 + 1/10

1/v = 25/250

v = 6 cm

Magnification = -v/u = -6/-10 = 0.6 < 1

Thus a diminished image is formed at a distance 6 cm behind the mirror.

Q13. The magnification produced by a plane mirror is +1. What does this mean?

As magnification = h’/h. A magnification of 1 means that the height of image is same as the height of object and a positive sign indicates that the image is virtual and erect.

Q14. An object 5 cm is placed at a distance of 20 cm in front of a convex mirror of radius of curvature 30 cm. Find the position, nature and size of the image.

Given h = 5 cm, u = -20 cm, R = 30 cm

As R = 2f

30 = 2f

f = 15 cm

Using mirror formula:

1/f = 1/v + 1/u

1/15 = 1/v – 1/20

1/v = 1/15 + 1/20

1/v = 35/300

v = 300/35 = 8.57 cm

Magnification m= -v/u = -8.57/-20 = 0.428

m = h’/h

0.428 = h’/5

h’ = 2.14 cm

As m < 1, v is positive and h’ < h, a virtual , erect and diminished image of size 2.14 cm is formed.

Q15. An object of size 7.0 cm is placed at 27 cm in front of a concave mirror of focal length 18 cm. At what distance from the mirror should a screen be placed so that a sharply focused image can be obtained? Find the size and nature of the image.

Given h = 7, u = -27 cm, f = -18 cm, v = ?

Using mirror formula:

1/f = 1/v + 1/u

-1/18 = 1/v – 1/27

1/v = -1/18 + 1/27

1/v = -1/54

v = -54 cm

Magnification m= -v/u = 54/-27 = -2

As m > 1 and has a negative sign, a real, inverted and magnified image of double the size of the object is formed at a distance of 54 cm in front of the mirror.

Q16. Find the focal length of a lens of power -2.0 D. What type of lens is this?

Given P = -2.0 D

We know that 1/f = P

1/f = -2

f = -1/2 = -0.5 m = -50cm

As the focal length is negative, it is a concave lens.

Q17. A doctor has prescribed a corrective lens of power +1.5 D. Find the focal length of the lens. Is the prescribed lens diverging or converging?

Given P = 1.5 D

We know that 1/f = P

1/f = 1.5

f = 1/1.5 = 0.667m

Thus the focal length is 0.667 m. As the focal length is positive, it is a convex lens which is converging lens.

Important Topics Discussed in NCERT Class 10 Science Chapter 10 Light – Reflection and Refraction

The topics covered in Chapter 10 ‘Light-Reflection and Refraction’ chapter in Class 10 NCERT Science are:

Key Features of NCERT Solutions for Class 10 Science Chapter 10 Light – Reflection and Refraction

• NCERT solutions are created by a team of professionals a GFG, with the intention to benefit students.
• These solutions are very accurate and comprehensive, which can help students prepare for any academic as well as competitive exam.
• All the solutions provided are in a step-by-step format for better understanding.

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NCERT Solutions for Class 10 Science Chapter 10 Light-Reflection and Refraction – FAQs

1. What is Reflection?

Reflection is the phenomenon where light, sound, or other waves bounce back when they encounter a surface that does not absorb them, obeying the law of reflection.

2. State the Law of reflection?

According to the law of reflection, the angle of incidence is equal to angle of reflection. It also states that the ray of incidence, normal to the plane of mirror, and the reflected ray all lie in the same plane.

3. What do you mean by irregular reflection?

Irregular reflection is a type of reflection in which the incident light reflects in different directions when it reflects from a rough or irregular surface.

4. What do you Mean by Regular Reflection?

Regular reflection is a type of reflection in which the incident light reflects at the same angle of incidence with the normal when it falls on a smooth surface or a plane mirror.

5. What is Refraction?

Refraction is the bending of light as it passes from one medium to another with a different optical density, causing the light to change direction and possibly speed.

6. What is the key Difference between Reflection and Refraction?

The key difference between reflection and refraction is that reflection involves the bouncing back of waves when they hit a surface, while refraction is the bending of waves as they pass from one medium to another due to a change in their speed and direction.

7. How does a Light Bend when it Passes from Rarer to Denser Medium?

Light bends towards the normal when it passes from rarer to denser medium.

8. What do you Mean by Focal Length of a Mirror?

Focal length of a mirror is defined as the distance between the pole of a mirror and its principal focus.