Friday, May 30, 2025

Optics

 

Concept Based

Q. 1. Why does a ray of light passing through the centre of curvature of a concave mirror gets reflected along same path after reflection?

 Q. 2. What kind of image is formed on a cinema screen?

 Q. 3. What do you mean by laterally inverted?

Q.4. What is the difference between virtual images produced by concave, plane and convex mirrors?

Q.5. For driving a car what type of mirror would you prefer to see the traffic at your back and why? Explain why it is preferred over a plane mirror?

Q.6 An erect image three times the size of the object is formed with a concave mirror of radius of curvature 36 cm. What is the position of the image?

Q.7. Discuss the position and nature of the image formed by a concave mirror when the object is moved from infinity towards the pole of mirror.

Q.8 Find the position, nature and size of the image of an object 3 cm high place at a distance of 9 cm from a concave mirror of focal length 18 cm.

Q.9. With the help of ray diagrams, show the formation of image of an object by a concave mirror. When it is placed: (i) beyond the centre of curvature (ii) at the centre of curvature.

MCQ

Q.1. Multiple images are formed by a thick plane mirror. Which of the following is the brightest of all the images?

A. First

B. second

C. third

D. fourth

Q. 2. A plane mirror is placed vertically facing due north. An arrow pointing north-east is kept in front of the mirror. In which direction will the arrow point in this image?

A. north-east

B. south-east

C. south-west

D. north-west

 

Q. 3. When a plane mirror is rotated through a certain angle, the reflected ray turns through twice as much and the size of the image:

A. is doubled

B. is halved

C. becomes infinite

D. remains same

Q.4. The image formed by a convex mirror is only one-third of the size of the object. If the focal length of the mirror is 12 cm, the image formed will be

A. 8 cm behind the mirror

B. 10 cm behind the mirror

C. 8 cm in front of the mirror

D. 10 cm in front of the mirror

Q.5. A beam of light incident on a plane mirror forms a real image on reflection. The incident beam is:

A. parallel

B. convergent

C. divergent

D. not certain

Q.6. If an object is placed symmetrically between two plane mirrors, inclined at an angle of 72°, then total number of images formed is:

A. 5

B. 4

C. 2

D. infinite

Q.7. A plane mirror produces a magnification of:

A. -1

B. + 1

C. zero

D. between 0 and infinity

Q. 8. A dice is place with one of its edges parallel to the principal axis between the principal focus and the centre of curvature of concave mirror. Then the final image has the shape of:

A. cube

B. rectangular parallelepiped

C. barrel shape

D. spherical

Q.9. Two adjacent walls and the ceiling of a rectangular room are mirror surfaced. The number of images of himself that an observer sees is:

A. 3

B. 9

C. 6

D. 8

 

Q. 10. Image formed by a convex spherical mirror is:

A. virtual

B. real

C. enlarged

D. inverted

Q.11. A diminished virtual image can be obtained only in:

A. plane mirror

B. concave mirror

C. convex mirror

D. all of these

Q. 12. A convex mirror has a focal length f. A real object is placed at a distance f in front of it. The mirror produces an image at:

A. infinity

B. f

C. f/2

D. 2f

Q. 13. A light ray incident normally on a plane mirror suffers deviation of:

A. zero

B. 90°

C. 180°

D. 360°

Q. 14. A convex mirror is used to form the image of a real object. Then tick the wrong statement:

A. image lies between the pole and the focus

B. image lies is diminished in size

C. image is erect

D. image is real

Q.15. An object is placed at a distance of 40 cm in front of a concave mirror of focal length 20 cm. The image produced is:

A. virtual and inverted

B. real and erect

C. real, inverted and diminished

D. real, inverted and of same size

Q. 16. Two plane mirrors are at right angles to each other. A man stands between them and combs his hair with the right hand. In how many images will he be seen using his left hand?

A. none

B. 1

C. 2

D. 3




 

Comprehensive Exercises (T/F)

1. Laws of reflection are true only for plane mirror and not for curved mirrors.

2.  The radius of curvature of a spherical mirror is half of the focal length.

3. The rays travelling parallel to the principal axis after reflecting from the concave mirror pass or appear to pass throng the focus.

4. Convex mirror can be used to see large image of small object.

5. A convex mirror always forms a virtual and erect image.

6. A concave mirror can be used to obtain a parallel beam of light from a small lamp.

7. A plane mirror can be used to form a real image equal in size as of the object.

8. A virtual, magnified and erect image can be formed by a concave mirror.

9. When a plane mirror is turned by a angle θ, the reflected rays turns by an angle θ.

10. In a plane mirror, the distance between image and the mirror is the same as distance between object and the mirror.

11. If an object is placed in between two plane mirrors inclined at and angle 45°, then the number of image formed will be 9.

12. Mirror formula is relation between height of the image and the height of the object.

13. Mirror formula is the same irrespective of convex mirror or a concave mirror.

14. Magnification equation is the same irrespective of convex mirror and concave mirror.



Number of Images ( in plane mirrors )