English Medium Class 10 - CBSE Question Bank Solutions for Science

1. A small object is placed 150 mm away from a diverging lens of focal length 100 mm.
   1. Copy the figure below and draw rays to show how an image is formed by the lens.
      
   2. Calculate the distance of the image from the lens by using the lens formula.
2. The diverging lens in part (a) is replaced by a converging lens also of focal length 100 mm. The object remains in the same position and an image is formed by the converging lens. Compare two properties of this image with those of the image formed by the diverging lens in part (a).

 The diverging lens in part (a) is replaced by a converging lens also of focal length 100 mm. The object remains in the same position and an image is formed by the converging lens. Compare two properties of this image with those of the image formed by the diverging lens in part (a).

A concave lens produces an image 20 cm from the lens of an object placed 30 cm from the lens. The focal length of the lens is:
(a) 50 cm
(b) 40 cm
(c) 60 cm
(d) 30 cm

Define the following terms in the context of spherical mirrors :
(i) Pole

(ii) Centre of curvature

(iii) Radius of curvature

(iv) Principal axis

An optical device has been given to a student and he determines its focal length by focusing the image of the sun on a screen placed 24 cm from the device on the same side as the sun. Select the correct statement about the device. 
(A) Convex mirror of focal length 12 cm
(B) Convex lens of focal length 24 cm
(C) Concave mirror of focal length 24 cm
(D) Convex lens of focal length 12 cm

AB and CD, two spherical mirrors, from parts of a hollow spherical ball with its centre at O as shown in the diagram. If arc AB = `1/2` arc CD, what is the ratio of their focal lengths? State which of the two mirrors will always form virtual image of an object placed in front of it and why.

A student obtained on a screen the sharp image of a candle flame placed at the farther end of laboratory table using a concave mirror. For getting better value of focal length of the mirror, the teacher suggested to him to focus the sun. What should the student do?
(A) Should move the mirror away from the screen.
(B) Should move the mirror towards the screen.
(C) Should move the mirror and screen both towards the sun.
(D) Should move only the screen towards the sun.

Mention the types of mirrors used as (i) rear view mirrors, (ii) shaving mirrors. List two reasons to justify your answers in each case.

A student obtained a sharp image of a burning candle, placed at the farther end of a laboratory table, on a screen using a concave mirror. For getting better value of focal length of the mirror, the subject teacher suggested him for focusing a well illuminated distant object. What should the student do?

(A) He should move the mirror away from the screen.

(B) He should move the mirror slightly towards the screen.

(C) He should move the mirror as well as the screen towards the newly selected object.

(D) He should move only the screen towards the newly selected object.

State the types of mirrors used for (i) headlights and (ii) rear view mirror, in cars and motorcycles. Give to justify your answer in each case.

Draw a ray diagram to show the formation of the image, when the object is placed between optical centre and principal focus of a convex lens.

State the signs and values of magnifications in the above mentioned case.

Answer the following question.
Write the modification in the curvature of the eye lens which enables us to see the nearby objects clearly?

In torches, search lights and headlights of vehicles the bulb is placed ______.

A student traces the path of a ray of light passing through a rectangular slab.

For measuring the angle of incidence, he must position the protractor in the manner shown in the figure:

An object is placed at a distance of 0.25 m
in front of a plane mirror. The distance between the object and image will be ______.

If the real image of a candle flame formed by a lens is three times the size of the flame and the distance between lens and image is 80 cm, at what distance should the candle be placed from the lens?

Name the type of mirror used in the following situation:

Side/rear-view mirror of a vehicle

Support your answer with reason.

Name the type of mirror used in the following situation:

Solar furnace

Support your answer with reason.

Define the following terms in the context of a diverging mirror:

1. Principal focus
2. Focal length

Draw a labelled ray diagram to illustrate your answer.