CBSE Class 10 Physics Reflection and Refraction of Light Worksheet Set B

LIGHT- REFLECTION AND REFRACTION

SECTION A

Assertion and Reason Type MCQs :

Following questions consists of two statements – Assertion (A) and Reason (R). Answer these questions selecting the appropriate option given below:
A. Both assertion and reason are true, and reason is the correct explanation of assertion.
B. Both assertion and reason are true, but reason is not the correct explanation of assertion.
C. Assertion is true but reason is false.
D. Assertion is false and reason is true.

Question. Assertion(A) : For observing traffic at back, the driver mirror is convex mirror.
Reason (R) : A convex mirror has much larger field of view than a plane mirror.

Answer: A

Question. Assertion (A): Higher the Refractive index of the medium lesser will be the speed of light in that Medium.
Reason (R): Refractive index is inversely proportional to the speed of light.

Answer: A

Question. Assertion (A): Refractive index of glass with respect to air is different for red light and violet light.
Reason (R): Refractive Index of a pair of medium does not depend on the wavelength of the light used.

Answer: C

Question. Assertion(A) : When the object moves with a velocity 2 m/s, its image in the plane mirror moves with a velocity of 4 m/s.
Reason (R) : The image formed by a plane mirror is as far behind the mirror as the object is in front of it.

Answer: A

Question. Assertion (A): Convex mirror is preferred for rear view mirrors in vehicles.
Reason (R) : The field view of a convex mirror is lesser than that of concave mirror.

Answer: C

Question. Assertion (A): Mirror Formula cannot be used for Plane Mirrors
Reason (R): Plane Mirror is a Spherical Mirror of Infinite Focal Length.

Answer: D

Question. Assertion (A) : It is impossible to see virtual image with our naked Eye
Reason (R) : The rays do not actually emanate from a virtual image.

Answer: D

Question. Assertion (A): A Concave mirror of radius R is placed in water .Its focal length differs in Air and Water.
Reason (R): Focal length of concave mirror is equal to R/2.

Answer: D

CASE BASED MCQs

I.  An image formed in a convex mirror is always virtual,erect and smaller in size whatever be the position of the object. However in a concave mirror the image may be real or virtual:
erect or inverted :smaller or bigger in size than the object. This would depend upon the distance of the object from the mirror.

Question. Which of the mirrors has larger field of view ?
A. Convex
B. Concave
C. plane
D. all have same field of view

Answer: A

Question. Real or virtual image of an object formed by a concave mirror depends on
A. Size of mirror
B. Polish of mirror
C. Distance of object from the mirror
D. All of these

Answer: C

Question. A Concave mirror is used as reflector in
A. Torches
B. Search lights
C. Head lights of motor vehicles
D. All the above

Answer: D

Question. In street lamps,the reflector used is a
A. Convex mirror
B. Concave mirror
C. Plane mirror
D. None of these

Answer: A

II. The image of an object formed by a convex lens may be real/virtual: erect/inverted; smaller/larger than the object. It would depend upon distance of the object from the lens. however, the image of an object formed by a concave lens is always virtual, erect and smaller in size than the object.

Question. Where should an object be placed in front or a convex lens to obtain image of the size of the object ?
A. At focus F
B. At 2 F
C. Beyond 2 F
D. None of these

Answer: B

Question. To obtain an image smaller than the size of the object, we may used a
A. Convex lens only
B. Concave lens only
C. Either a convex lens or a concave lens
D. Cannot say

Answer: C

Question. to obtain image of an object on a screen jwe require a
A. Convex lens
B. Concave lens
C. Concave lens of large focal length
D. Concave lens of small focal length

Answer: A

Question. Where an object should be placed in front of a concave lens to obtain a virtual image of the object?
A. Infinity
B. Principal focus
C. Very close to the lens
D. Any distance from the lens

Answer: D

III. The scattering involves bouncing off of light by atoms/molecules of the medium through which they are travelling. Most of the beautiful phenomena like blue colour of sky, white colour of clouds, red hues of sunrise and sunset have been explained in terms of scattering of light. Lord Rayleigh studied elastic scattering and established that intensity of scattered light (Is) varies inversely as the fourth power of wavelength (ℷ) of incident light. The only condition for Rayleigh scattering to be valid is that size of scatterer (x) must be much less than the wavelength (ℷ) of light.

Question. In Rayleigh scattering intensity of scattered light (Is) varies inversely as power (n) of wave length (ℷ) of light, where n =
A. 6
B. 8
C. 4
D. 2

Answer: C

Question. Rayleigh scattering accounts for
A. Blue colour of sky
B. White colour of clouds
C. Red hues of sun rise and sun set
D. All the above

Answer: B

Question. Rayleigh scattering accounts for
A. Blue colourof sky
B. White colour of clouds
C. Red hues of sunrise and sunset
D. All the above

Answer: C

Question. The essential condition for rayleigh’s scattering is the size (x) of scatterer must be
A. Much smaller wave length (ℷ) of light
B. Much grater then the wave length of light
C. Equal to wave length of light
D. Cannot say

Answer: D
 

• CONCEPTUAL QUESTION

1 The refractive index of carbon disulphide is 1.63. What is the meaning of this statement?

2 A person wants to see the full length image of tall building in a small mirror. Which type of mirror should be used by him?

3 Distinguish between real and virtual images.

4 A ray of light travelling in air enters obliquely into water. Does the light ray bend towards or away from the normal? Why?

5 What is lateral displacement of light? State the factors affecting it

6 Define the following terms in the context of spherical mirrors:

(i) Pole

(ii) Centre of curvature

(iii) Radius of curvature

(iv) Principal axis

7 Under what condition will a glass lens placed in a transparent liquid becomes invisible?

8 Draw a ray diagram and also state the nature of the image formed by concave mirror when the object is placed at the centre of curvature.

9 Draw a diagram to show dispersion of white light by a glass prism. Label the coloures that appear at the two ends of the colour band. State the reason why different coloured rays deviate differentially in the prism.

10 With a help of a ray diagram, state the meaning of refraction of light. State Snell’s law of refraction of light and also express it mathematically.

11 Given below are the refractive indices of a few media. Identify the media in which the speed of light will be highest and lowest respectively.

medium                   Refractive Index
Diamond                2.42
glass                      1.5
water                     1.3
Kerosene oil           1.4

12 Identify the nature of spherical mirror or of lens in the following cases, and draw ray diagrams for each case.

(a) When object is placed between mirror and its focus, image formed is erect, enlarged and behind it.

(b) When object is placed at 2F of the lens image formed is diminished, erect, and the same side of the lens as that of the object.

13 Can refractive index of a medium be less than unity? What is the value of refractive index of vacuum?

14 Why does a light ray incident on a rectangular glass slab immersed in any medium emerges parallel to itself? Explain using a diagram.

15 For a concave mirror draw ray diagram to show the reflected ray when ray of light incident obliquely on the pole of the mirror.

Section B

Numerical problems

16 A student focused the image of candle flame on a white screen using a convex lens. He noted down the position of the candle, screen and the lens as under

i) position of candle is 12.6cm

ii) position of convex lens is 51.8cm

iii) position of screen is 91.0cm

a) calculate the focal length of the lens

b) Where will the image be formed if he shifts the candle towards the candle at a position of 32.2cm?

c) What will be the nature of the image if he shifts the candle further towards the lens?

d) Draw a ray diagram to show the formation of the image in case © as said above

17 The image of a candle flame placed at a distance of 45cm from a spherical lens is formed on a screen placed at a distance of 90cm from the lens. Identify the type of lens and calculate its focal length. If the height of the flame is 2cm, find the height of its image.

18 At what distance should an object be placed from a convex lens of focal length 18cm to obtain an image at 24cm from it on the other side. What will be the magnification produced in this case?

19 An object of height 6cm is placed perpendicular to the principal axis of a concave lens of focal length 5cm. Determine the position, size and nature of the image if the distance of the object from the lens is 10cm.

20 An object is kept at a distance of 18cm, 20cm 22cm and 30cm from a lens of power +5D.

(a) In which case or cases would you get magnified image?

(b) Which of the magnified image can be got on a screen?

21 Analyse the following observation table showing variation of image distance (v) with object distance(u) in case of convex lens and answer the questions that follow without doing any calculations:

a) What is the focal length of the convex lens? State reason for your answer.

b) For what object distance is the corresponding image distance not correct? How did you arrive at this conclusion?

c) Choose an appropriate scale to draw a ray diagram for the observation at S.NO 4 and find the approximate value of magnification.

22 A spherical mirror produces an image of magnification m= -1 on a screen placed at a distance of 50cm from the mirror.

(a) Write the type of mirror.

(b) Find the distance of the image from the object.

(c) What is the focal length?

(d) Draw the diagram to show the image formation in this case.

23 A student has focused the image of a candle flame on a white screen using a concave mirror. The situation is as given below: Length of the flame= 1.5cm

Focal length of the mirror = 12cm

Distance of flame from the mirror= 18cm

Calculate the following:

(a) Distance of the image from the mirror

(b) Length of the image

(c) If the distance between the mirror and the flame is reduced to 10cm, then what would be observed on the screen? Draw ray diagram to justify your answer for this situation.

24 (a) A concave mirror produces 3 times enlarged image of an object placed at 10cm in front of it. Calculate the focal length of the mirror.

(b) Show the formation of the image with the help of a ray diagram when an object is placed 6cm away from the pole of the mirror.

25 The refractive index of a dense flint glass is 1.65 and for alcohol it is 1.36 with respect to air. Find the refractive index of dense flint glass with respect to alcohol.

26 If the image formed by a spherical mirror for all positions of the object placed in front of it is always erect and diminished, what type of mirror is it? Draw a labeled ray diagram to support your answer. (Board question 2017-18)

27 State the laws of refraction of light. Explain the term ‘absolute refractive index of a medium’ and write an expression to relate it with the speed of light in vacuum. (Board question 2017-18)

28 What is meant by power of lens? Write its SI unit. A student uses a lens of focal length 40cm and another of -20cm. Write the nature and power of each lens.
 Board question 2017-18)

29 An object of height 4.0cm is placed at a distance of 30cm from the optical centre ‘O’ of convex lens of focal 20cm. Draw a ray diagram to find the position and size of the image formed. Mark optical centre ‘O’ and principal focus ‘F’ on the diagram. Also find the approximate ratio of size of the image to the size of the object. (Board question- Section B- 2017-18)

 

Please click on below link to download CBSE Class 10 Physics Reflection and Refraction of Light Worksheet Set B