physics - light - reflection and refraction

Class 10 - Physics

Light - Reflection and Refraction

MCQ
Q&A
Question:

Define the focus of a concave mirror. If the radius of curvature of a convex mirror is 30 cm, what would be its focal length? [Foreign]

Answer:

The point on the principal axis where all the rays parallel to it meet after reflection is called focus. Since, R = 30 cm and f=R/2 we have, f=+15 cm for a convex mirror.



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Questions and Answers


Light - Reflection and Refraction - Questions
1.

Define one dioptre of power of a lens?


Answer
2.

A ray of light enters a rectangular glass slab of refractive index 1.5. It is found that the ray emerges from the opposite face of the slab without being displaced. If its speed in air is 3 x 108 ms-1 then what is its speed in glass? [Foreign]


Answer
3.

An object is placed between infinity and the pole of a convex mirror. Draw a ray diagram and also state the position, the relative size and the nature of the image formed. [All India]


Answer
4.

Redraw the given diagram and show the path of the refracted ray: [All India(C)]
light-reflection-and-refraction-chapter-wise-important-questions-class-10-science-13


Answer
5.

Which kind of mirrors are used in the headlights of a motor-car and why? [Foreign]


Answer
6.

Explain with the help of a diagram, why a pencil partly immersed in water appears to be bent at the water surface. [Delhi]


Answer
7.

An object 2 cm high is placed at a distance of 64 cm from a white screen. On placing a convex lens at a distance of 32 cm from the object it is found that a distinct image of the object is formed on the screen. What is the focal length of the convex lens and size of the image formed on the screen? Draw a ray diagram to show the formation of the image in this position of the object with respect to the lens. [Delhi(C)]


Answer
8.

A convex lens has a focal length of 10 cm. At what distance from the lens should the object be placed so that it forms a real and inverted image 20 cm away from the lens? What would be the size of the image formed if the object is 2 cm high? With the help of a ray diagram show the formation of the image by the lens in this case. [All India (C)]


Answer
9.

The refractive index of glass is 1.50 and the speed of light in air is 3 x 108 ms-1. Calculate the speed of light in glass. [Foreign]


Answer
10.

For which position of the object does a convex lens form a virtual and erect image? Explain with the help of a ray diagram. [All India]


Answer
11.

A girl was playing with a thin beam of light from her laser torch by directing it from different directions on a convex lens held vertically. She was surprised to see that in a particular direction the beam of light continues to move along the same direction after passing through the lens. State the reason for this observation. [Foreign]


Answer
12.

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


Answer
13.

The radius of curvature of a spherical mirror is 20 cm. What is its focal length?


Answer
14.

A concave mirror produces three times magnified (enlarged) real image of object placed at 10 cm in front of it. Where is the image located?


Answer
15.

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 sharp focused image can be obtained? Find the size and the nature of the image.


Answer
16.

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?


Answer
17.

Draw the ray diagram in each case to show the position and nature of the image formed when the object is placed:
(i) at the centre of curvature of a concave mirror
(ii) between the pole P and focus F of a concave mirror
(iii) in front of a convex mirror
(iv) at 2F of a convex lens
(v) in front of a concave lens


Answer
18.

“The refractive index of diamond is 2.42”. What is the meaning of this statement in relation to speed of light? [Delhi]


Answer
19.

The refractive index of water is 1.33 and the speed of light in air is 3 x 108 ms-1. Calculate the speed of light in water. [Foreign]


Answer
20.

Explain why a ray of light passing through the centre of curvature of a concave mirror, gets reflected along the same path. [Delhi]


Answer
21.

“The refractive index of carbon disulphide is 1.63.” What is the meaning of this statement in relation to speed of light? [Delhi]


Answer
22.

List four properties of the image formed by a plane mirror. [Delhi]


Answer
23.

List four properties of the image formed by a concave mirror, when object is placed between focus and pole of the mirror. [Delhi]


Answer
24.

A 6 cm tall object is placed perpendicular to the principal axis of a convex lens of focal length 15 cm. The distance of the object from the lens is 10 cm. Find the position, size and nature of the image formed, using the lens formula. [Foreign]


Answer
25.

List the sign conventions that are followed in case of refraction of light through spherical lenses. Draw a diagram and apply these conventions in determining the nature and focal length of a spherical lens which forms three times magnified real image of an object placed 16 cm from the lens. [Foreign]

 


Answer
26.

A convex lens forms a real and inverted image of a needle at a distance of 50 cm from it. Where is the needle placed in front of the lens if the image is equal to the size of the object? Also find the power of the lens.


Answer
27.

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


Answer
28.

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 ¡mage.


Answer
29.

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


Answer
30.

The refractive indices of four media A, B, C and D are given in the following table:
light-reflection-and-refraction-chapter-wise-important-questions-class-10-science-9
If light, travels from one medium to another, in which case the change in speed will be (i) minimum, (ii) maximum? [Delhi(C)]


Answer
31.

Redraw the given diagram and show the path of the refracted ray: [All India(C)]
light-reflection-and-refraction-chapter-wise-important-questions-class-10-science-11


Answer
32.

An object 2 cm in size is placed 30 cm in front of a concave mirror of focal length 15 cm. At what distance from the mirror should a screen be placed in order to obtain a sharp image? What will be the nature and the size of the image formed? Draw a ray diagram to show the formation of the image in this case. [Delhi(C)]


Answer
33.

Between which two points related to a concave mirror should an object be placed to obtain on a screen an image twice the size of the object? [All India]


Answer
34.

How far should an object be placed from a .convex lens of focal length 20 cm to obtain its image at a distance of 30 cm from the lens? What will be the height of the image if the object is 6 cm tall? [All India]


Answer
35.

Draw a ray diagram and also state the position, the relative size and the nature of image formed by a concave mirror when the object is placed at the centre of curvature of the mirror. [Delhi]


Answer
36.

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


Answer
37.

An object 50 cm tall is placed on the principal axis of a convex lens. Its 20 cm tall image is formed on the screen placed at a distance of 10 cm from the lens. Calculate the focal length of the lens. [All India]


Answer
38.

If a light ray IM is incident on the surface AB as shown, identify the correct emergent ray. [Delhi (C)]

light-reflection-and-refraction-chapter-wise-important-questions-class-10-science-8


Answer
39.

A ray of light, incident obliquely on a face of a rectangular glass slab placed in air, emerges from the opposite face parallel to the incident ray. State two factors on which the lateral displacement of the emergent ray depends. [Foreign]


Answer
40.

A convex lens has a focal length of 10 cm. At what distance from the lens should the object be placed so that it forms a real and inverted image 20 cm away from the lens? What would be the size of the image formed if the object is 2 cm high? With the help of a ray diagram show the formation of the image by the lens in this case. [All India (C)]


Answer
41.

Redraw the diagram given below in your answer book and show the direction of the light ray after reflection from the mirror. [Delhi (C)]
light-reflection-and-refraction-chapter-wise-important-questions-class-10-science-23


Answer
42.

What is the minimum number of rays required for locating the image formed by a concave mirror for an object. Draw a ray diagram to show the formation of a virtual image by a concave mirror. [Delhi]


Answer
43.

Between which two points of a concave mirror should an object be placed to obtain a magnification of -3? [Delhi]


Answer
44.

Draw the ray diagram and also state the position, relative size and nature of the image formed by a concave mirror when the object is placed between its centre of curvature, C and focus, F. [Foreign]


Answer
45.

List four properties of the image formed by a convex mirror. [Delhi]


Answer
46.

Find the focal length of a convex mirror whose radius of curvature is 32 cm.


Answer
47.

Light enters from air to glass having refractive index 1.50. What is the speed of light in the glass? The speed of light in vacuum is 3 × 108 m/s.


Answer
48.

Draw ray diagrams to represent the nature, position and relative size of the image formed by a convex lens for the object placed:
(a) at 2F1
(b) between F1 and the optical centre O of lens: [All India]


Answer
49.

Redraw the diagram given below in your answer book and show the direction of the light ray after refraction from the lens. [Delhi, All India(C)]
light-reflection-and-refraction-chapter-wise-important-questions-class-10-science-29


Answer
50.

Redraw the diagram given below in your answer book and show the direction of the light ray after refraction from the lens. [All India (C)]
light-reflection-and-refraction-chapter-wise-important-questions-class-10-science-31


Answer
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