Ray Optics And Optical Instruments

Previous Years' CBSE Board Questions

9.2 Reflection of Light by Spherical Mirrors

Focal Length of Spherical Mirrors

(5 marks)

1 Define the term 'focal length of a mirror'. With the help of a ray diagram, obtain the relation between its focal length and radius of curvature. (2020)

The Mirror Equation

(b) Suppose the lower half of the concave mirror's

reflecting surface is covered with an opaque

material. What effect this will have on the image

of the object? Explain. (Delhi 2014) Ap

LA (5 marks)

An object is placed in front of a concave mirror. It is

observed that a virtual image is formed. Draw the

ray diagram to show the image formation and hence

derive the mirror equation <math>\frac{1}{f} = \frac{1}{u} + \frac{1}{v}</math>. (3/5, 2020)

(a) Draw a ray diagram to show image formation

VSA (1 mark)

2 When an object is placed between f and 2f of a concave mirror, would the image formed be (i) real or virtual and (ii) diminished or magnified?

(Delhi 2015C) (U

SAI (2 marks)

1. An object is kept 20 cm in front of a concave mirror of radius of curvature 60 cm. Find the nature and position of the image formed. (2020)
2. An object is kept in front of a concave mirror of focal length 15 cm. The image formed is real and three times the size of the object. Calculate the distance of the object from the mirror. (AI 2019)
3. Use the mirror equation to show that an object placed between f and 2f of a concave mirror produces a real image beyond 2f. (Delhi 2015)

SAII (3 marks)

1. A concave mirror produces a two times enlarged virtual image of an object kept 10 cm away from the mirror.
2. Find the focal length of the mirror.
3. By how much distance the object be displaced and in what direction, in order to get two times enlarged real image of the object? (2020)
4. (a) Calculate the distance of an object of height h from a concave mirror of radius of curvature 20 cm, so as to obtain a real image of magnification 2. Find the location of image also.
5. Using mirror formula, explain why does a convex mirror always produce a virtual image.

(Delhi 2016) Ap

Water Water

1. (a) A mobile phone lies along the principal axis of a concave mirror. Show, with the help of a suitable diagram, the formation of its image. Explain why magnification is not uniform.

18° 18°

Air Air В Water Water 60° C (c) (d)

18° 18° (Foreign 2014) U SAI (2 marks)

1. A point source of light is placed at the bottom

when the concave mirror produces a real,

inverted and magnified image of the object.

(b) Obtain the mirror formula and write the expression

for the linear magnification. (4/5, 2018) An

9.3 Refraction

SAII (3 marks)

Monochromatic light of wavelength 589 nm is

incident from air on a water surface. If <math>\mu</math> for water

is 1.33, find the wavelength, frequency and speed of

the refracted light. (2/3, Al 2017) (Ap)

9.4 Total Internal Reflection

MCQ

Here, question 12 (i) to (v) is a case study base question

of 5 marks.

A ray of light travels from a denser to a rarer medium.

After refraction, it bends away from the normal.

When we keep increasing the angle of incidence, the

angle of refraction also increases till the refracted

ray grazes along the interference of two media. The

angle of incidence for which it happens is called

critical angle. If the angle of incidence is increased

further the ray will not emerge and it will be reflected

back in the denser medium. This phenomenon is

called total internal reflection of light.

(i) A ray of light travels from a medium into water

at an angle of incidence of 18°. The refractive index

of the medium is more than that of water and the

critical angle for the interface between the two

media is 20°. Which one of the following figures best

represents the correct path of the ray of light? (a) (b)