Light Q Bank

PRAYAS STUDY MATERIAL QUESTION BANK (LIGHT) VERY SHORT ANSWER QUESTIONS (1 MARK) 1.

What focal length can be assigned to a plane mirror?

2.

If the magnification of a body of size 1m is 2 what is the size of the image?

3.

Where will the image be formed by a convex mirror if the object is placed between

infinity and the pole of the mirror? 4.

What is the power of concave lens of focal length 25cm?

5. What will be the focal length of a lens of power +2D? 6. Name the mirror which gives an erect and enlarged image of an object. 7. The focal length of a thin lens is given by f=-10cm. Name the type of the lens. 8. When a ray of light passes from medium 1 to medium 2 it bends away from the normal. Which of the two is the optically denser medium? 9. Define the unit of power of a lens. 10. What is the focal length of a concave lens whose power is -1.5 D?

SHORT ANSWER QUESTIONS (2 MARKS) 1.

Give the characteristics of image formed by a plane mirror?

2.

With respect to air the refractive indices of water and benzene are

1.33 and 1.5 respectively. Calculate the refractive of benzene with respect to water 3.

An object is placed at a point 0.06m from a convex lens of focal length 0.1m.

Calculate the position of the image 4.

Light enters from air into a glass plate which a refractive index of 1.5 calculate

the speed of light in glass. the speed of light in air is 3x108 m/sec 5.

Draw a ray diagram to show the position and nature of image formed when an

object is placed between focus F and pole P of concave of a concave mirror. 6.

Why do we prefer a convex mirror as a rear view mirror?

7.

The absolute refractive index of diamond is 2.42.What is the velocity of light in diamond?

8.

Assuming the Principal axis as the x axis and the optical centre as the origin, how will you determine the sign of the quantities U, V and f for a lens?

9.

A ray of light traveling in air is incident on the plane surface of transparent medium. The angle of incidence is 450 and that of refraction is 300 . Find the refractive index of the medium.

10. With the help of ray diagram find the position of image when the object is kept between infinity and the optical centre of convex mirror.

SHORT ANSWER QUESTIONS (3 MARKS) 1.

An object of 3cm height is placed at a distance of 10 cm in front of a concave of focal length 20cm.Find the position ,nature and size of image formed

2.

An object is placed at a distance of 12cm in front of a concave mirror. It forms a real image 4 times larger than the object. Calculate the distance of the image from the mirror.

3.

Draw a ray diagram to show the formation of the image of an object by a convex mirror when it is placed (1)at infinity(2)between infinity and pole of the mirror

4.

(a) State Snell’s law of refraction of light (b)A transparent medium A floats on another transparent medium B. when a ray of light travels obliquely from A to B the refracted ray bends away from the normal. Which of the media A and B is optically and denser and why?

5.

Draw a labeled diagram to locate the image of an object formed by a convex lens of focal length 20cm when the object is placed 30cm away from the lens

6.

Define the terms focus, pole, principal axis, centre of curvature, radius of curvature and focal length of spherical mirror.

7.

Write and explain various uses of convex and concave mirror.

8.

Show with neat ray diagram light emerges from rectangular glass slab in a direction parallel to that in which it entered the glass slab.

9.

Tabulate the position and nature of the image formed by a convex lens for various possible positions of the object.

10. Tabulate the position and nature of the image formed by a concave mirror for various possible positions of the object.

LONG ANSWER QUESTIONS (5 MARKS) 1.

(a)State the relation between object distance, image distance and focal length of a spherical mirror. (b)Draw a ray diagram to show the image formed by a concave mirror when an object is placed between pole and focus of the mirror (c)A concave mirror of focal length 15cm forms an image of an object kept at a distance of 10cm from the mirror. Find the position, nature, and size of the image formed by it

2.

(a )Draw a ray diagram to show the passage of light through a rectangular glass slab ,when the angle of incidence is zero in one case and a little less than 90 degree in the other case. (b)Prove that if a ray enters a rectangular slab obliquely and emerges from the opposite face, the emergent ray will be parallel to the incident ray

3.

4.

Draw the ray diagram to show the formation of image by a concave mirror when the object is kept. a)

beyond C

b)

between C and F.

c)

at C

d)

at F

e)

between F and P

An object of size 10 cm is placed in front of a convex lens of focal length 50 cm. Find nature, size, and position of the image when the object is placed at a)25cm and b)100cm.

Numerical problems 1.

A concave mirror is made by cutting a portion of a hollow glass sphere of radius 24 cm. Find the focal length of the mirror.

2.

An object is placed at a distance of 10 cm from a concave mirror of focal length 20cm

3.

4.

a)

Draw the ray diagram for the formation of image

b)

Calculate the image distance

c)

State two characteristics of image formed.

A 1.2 cm long pin is placed perpendicular to the principal axis of a convex mirror of focal length 12 cm at a distance of 8 cm from it. a)

Find the location of the image

b)

Find the height of the image

c)

Is the image erect or inverted?

Find the refractive index of glass with respect to water. The refractive indices of these w.r.t air are 3/2 and 4/3 respectively. An object is placed before a concave lens of focal length 12cm. The size of the image formed by the lens is half the size of the object. Calculate the distance of the object from the lens.