NIOS Class 10 Science and Technology Chapter 15 Light Energy

NIOS Class 10 Science and Technology Chapter 15 Light Energy Solutions to each chapter is provided in the list so that you can easily browse through different chapters NIOS Class 10 Science and Technology Chapter 15 Light Energy and select need one. NIOS Class 10 Science and Technology Chapter 15 Light Energy Question Answers Download PDF. NIOS Study Material of Class 10 Science and Technology Notes Paper 212.

NIOS Class 10 Science and Technology Chapter 15 Light Energy

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Also, you can read the NIOS book online in these sections Solutions by Expert Teachers as per National Institute of Open Schooling (NIOS) Book guidelines. These solutions are part of NIOS All Subject Solutions. Here we have given NIOS Class 10 Science and Technology Chapter 15 Light Energy, NIOS Secondary Course Science and Technology Solutions for All Chapters, You can practice these here.

Light Energy

Chapter: 15

INTEXT QUESTIONS 15.1

1. In column A, some sources of light are given. In column B, you have to write whether these are luminous or non-luminous.

Ans: 

2. Write two differences between real and virtual image.

Ans: Two difference between real and virtual image are mentioned below: 

3. When you are standing in front of a plane mirror, a virtual and correct image of you is formed. If some one is taking a photograph of it using camera, what will be the nature of the image on photograph?

Ans: Real.

4. A light ray is falling on a plane mirror at 30° as shown in the diagram. If the plane mirror is rotated by 30° without changing the direction of the incident ray, by what angle the reflected ray will rotate?

Ans: 60° .

5. An object of height 10 cm is placed in front of a plane mirror of height 8 cm. What will be the height of the image formed? Taking the distance of the object from the mirror 6 cm, draw the ray diagram.

Ans:                     

6. The image of an object placed at 10 cm from the mirror is formed at 10 cm behind the mirror. If the object is displaced by 4 cm towards the mirror, by what distance will the image be displaced with respect to the 

(i) Mirror.

Ans: 4 cm.

(ii) Object?

Ans: 8 cm.

7. An object is moving with velocity 6 ms–1 towards a plane mirror, what will be the velocity of image towards the

(i) mirror.

Ans: 6.0 ms–¹.

(ii) Object? 

Ans: 12.0 ms–¹.

8. Some letters are given in the following boxes. Make meaningful words related to reflection of light choosing the horizontal and vertical sequencing.

Ans: Real, Erect, Plane, Virtual, Image.

9. The distance and height of an object placed in front of a plane mirror are given in column A and B respectively. In column C and D the distance of image and height of image are given but not in same order. Correct the order. 

Ans: 

INTEXT QUESTIONS 15.2

1. An object is placed in front of a concave mirror as shown in the Fig. 15.16. Write the position and nature of the image. What is the focal length of the mirror?

Ans: Position is equal to 8.55 cm, the image is real of focal length 5 cm.

2. In what condition, the image formed by a concave mirror is virtual?

Ans: When the object is between the focal point and pole of the mirror then the image will be formed in the concave mirrors.

3. At what position will the reflected ray shown in Fig. 15.17 intersect the principal axis beyond focus or before focus?

Ans: Before focus.

4. What type of image will be formed if an object is placed beyond centre of curvature in front of a concave mirror?

Ans: Real, smaller in size and inverted.

5. Find the position of the object placed in front of a concave mirror of focal length 20 cm if image is formed at the distance of 30 cm from the mirror.

Ans: 60 cm in front of mirror.

6. Write two uses of concave mirror.

Ans: Saving mirror, magnifying mirror for dentist.

7. Write the nature of image formed in convex mirror.

Ans: Always virtual and smaller in size.

8. Find the position of the image formed in convex mirror of focal length 12 cm when object is placed at the distance of 

(i) 8 cm.

Ans: As we know, 1/f = 1/v + 1/u,

In case 1, f = 12cm, u = – 8cm,

So, 1/12 = 1/v – 1/8;

Or, v = 4.8cm.

(ii) 12 cm.

Ans: f =12cm, u = – 12cm.

So, 1/12 = 1/v + 1/(-12) ;

Or, v = 6cm. 

(iii) 18 cm from the mirror.

Ans: f = 12cm, u = – 18cm,

So, 1/12 = 1/v – 1/18;

Or, v = 7.2cm.

9. Complete the following table with corresponding positions of object and image in case of concave mirror.

Ans:

INTEXT QUESTIONS 15.3

1. Name the type of lens which always produces virtual images.

Ans: Concave lens.

2. Draw the ray diagram for the image formation in convex lens where object is placed at 

(i) F. 

Ans: 

(ii) Between F and 2F.

Ans: 

(iii) Beyond 2F.

Ans: 

3. Draw the ray diagram for image formation in concave lens.

Ans:

4. The sizes of the image and object are equal in a lens of focal length 20 cm. Name the type of lens and distance of object from the lens.

Ans: Convex lens, 40 cm.

5. An object of size 10 cm is placed in front of convex lens of focal length 20 cm. Find the size of the image formed.

Ans:  –20 cm.

INTEXT QUESTIONS 15.4

1. When light passes from air to a medium its speed reduces to 40%. The velocity of light in air is 3 × 108 ms-1. What is the refractive index of the medium?

Ans: 5/3.

2. When sunlight is passed through prism, it splits into seven colours as shown in Fig. By numbers write corresponding colours.

Ans: The lens must be convex lens. The distance of object from the lens will be at 2F or 2×20 or 40cm.

3. How do r and δ change for same angle of incidence i if the prism shown in Fig. is immersed in water.

Ans: r and δ both will decrease.

4. Why does white light split into seven colours when it passes through a prism?

Ans: Material of the prism has different value of refractive index for different colours of light.

5. Write a natural phenomenon of dispersion of light:

Ans: Rainbow in the sky.

INTEXT QUESTIONS 15.5

1. Identify the eye having defective vision from the following diagrams. Write the type of defect in vision. How this defect can be removed?

Ans: Do your self.

2. Three students Riya, Tiya and Jiya in a class are using sphericals of power + 2D, +4D and –2D. What type of defect in vision they have?

Ans: Riya and Tiya have longsightedness and Jiya has shortsightedness.

3. How does the focal length of the eye changes when a lens is used to correct the defect of vision in case of

(i) short sightedness and 

Ans: Increases.

(ii) long or for sightedness.

Ans: Cecrease.

1. What happens to the speed of light when it goes from

(i) Denser medium to rare medium.

Ans: The speed of the light will be increase when it travels from denser to rarer medium.

(ii) Rarer medium to denser medium?

Ans: The speed of light will decrease when the light travels from rarer to denser medium.

2. Can angle of incidence be equal to the angle refraction? Justify.

Ans: The angle of incidence and angle of refraction are the same, only when the incident rays enter the interface of two different media at right angles to the interface i.e. the angle of incidence is zero. In this case the angle of refraction is also zero.

3. Does a convex lens always converge light? Explain.

Ans: A convex lens is also known as a converging lens. 

It is called so because it has a surface which is curved outside and when the parallel beam of light falls on it converges at one point. Hence, a concave lens diverges rays of light whereas a convex lens converges rays of light.

4. Write the nature of the image formed by a concave lens.

Ans: A concave lens always forms a virtual image.

5. In horizontal and vertical boxes of the letter grid some meaningful words regarding the properties of light are placed in different rows and column in the table below. Find at least three and define them? 

Ans: DO yourself.

6. What will be the nature of the image formed in a convex mirror and in a concave mirror each of focal length 20 cm and object is placed at the distance of 10 cm.

Ans: From mirror formula, 1/f = 1/v + 1/u;

Here, v= ? u = – 10cm, f = 20cm.

So, 1/20 = 1/v –1/10;

Or, v = 6.66cm.

7. Find the position of the image formed in concave mirror of focal length 12 cm when object is placed 20 cm away from the mirror. Also find magnification.

Ans: From mirror formula, 1/f = 1/ v + 1/u;

F = 12cm, u =- 20cm, v = ?

So, 1/12 = 1/v – 1/20;

Or, v = 60/8 cm.

Then magnification is (m = – v/u = 60/8 ÷ 20 = 0.25.

8. In which of the following media, the speed of light is maximum and in which it is minimum.

Ans:  DO yourself.

9. The image of a candle formed by a convex lens is obtained on a screen. Will full size of the image be obtained if the lower half of the lens is printed black and completely opaque? Illustrate your answer with a ray diagram.

Ans: 

10. Can a single lens ever form a real and erect image?

Ans:  A real and erect image is not possible from a single lens.For a real object, it is not possible for a single lens to form a real and erect image. But for a virtual object, it may be possible.

11. What is dispersion of light? What is the cause of dispersion of light?

Ans: Dispersion of light is the splitting of white light into its constituent colours due to the refractive index of the surface and the wavelength of the light. If the light entering the prism is not of a single colour then the emergent beam also has different colours arranged in a definite order.

The basic reason behind the dispersion of white light into seven different colours is because all the seven rays of light of different colours travel at different speeds through the glass prism.

12. Why do distant objects appear to be smaller and closer to each other?

Ans: When things are closer to you, they take up more of your field of view, so they seem bigger. When they’re further away, they take up less of your field of view, and so seem smaller. One way to measure our field of view is to use an angle. An angle is a measure of how much something turns, and it’s measured in degrees.

13. A person looking at a net of crossed wires is able to see the vertical direction more distinctly than the horizontal wires. What is the defect due to? How is such a defect of vision corrected? 

Ans: The person looking at a net of crossed wires is able to see the vertical direction more distinctly than the horizontal wires this problem occurs because of the defect of cornea and eye lens and this problem know as astigmatisms.

14. A person can see the objects placed at a distance of 30 cm clearly but cannot see the objects placed 30 m away. What type of defect of vision he has? How is this defect of vision corrected?

Ans: Do yourself.

15. Distinguish visible, ultraviolet and infrared light.

Ans: The visible part of the electromagnetic spectrum only covers a small range of wavelengths, from 380 nm to 750 nm. In the electromagnetic spectrum, shorter wavelengths (from 10 nm to 380 nm) are ultraviolet (UV) and longer wavelengths (from 750 nm to 1 mm) are infrared (IR) radiation.

16. Which of the following quantities remains constant during reflection of light? 

(i) speed of light.

(ii) frequency of light.

(iii) wavelength of light.

Ans: (ii) frequency of light.

17. Write the value of angle of reflection at both the reflecting surfaces M1 and M2 held perpendicular to each other as shown in Fig. 15.34. 

Ans: Do yourself.

18. An object is placed in front of a plane mirror. The mirror is moved away from the object with the speed of 0.25 ms–1. What is the speed of the image with respect to the mirror and with respect to the object?

Ans: Do yourself.

19. Size of the image in a plane mirror of height 12 cm is 20 cm. What is the size of the object?

Ans: The image is always virtual, erect and of the same shape and size as the object. Size of the object is 20 cm.