ray optics theory part

Question 1

Write the laws of reflection

Answer 1

1)The angle of incidence is equal to the angle of reflection(i=r).
2)The incident ray, reflected ray and the normal to the reflecting
surface at the point of incidence lie in the same plane.

Question 2

Write the Cartesian sign convention to measure distances.

Answer 2

1) All distances are measured from the pole of the mirror or the optical
centre of the lens.
2) The distances measured in the same direction as the incident light are
taken as positive and those measured in the direction opposite to the
direction of incident light are taken as negative.
3) The heights measured upwards with respect to principal axis of the
mirror/ lens are taken as positive .The heights measured downwards
are taken as negative.

Question 3

mirror formula

Answer 3

1/v+1/u=1/f

Question 4

magnification of mirror

Answer 4

-v/u=m

Question 5

State the laws of refraction

Answer 5

(i) The incident ray, the refracted ray and the normal to the interface at the point of incidence, all lie in the same plane.
(ii) The ratio of the sine of the angle of incidence to the sine of angle
of refraction is constant.(Snell’s Law)

𝐬𝐢𝐧 𝒊/𝐬𝐢𝐧 𝒓 = 𝒏𝟐𝟏

Question 6

What is total internal reflection ?

Answer 6

When a ray of light enters from a denser medium to a rarer medium, if the
angle of incidence is greater than the critical angle (ic) for the given pair of
media, the incident ray is totally reflected. This is called total internal
reflection

Question 7

What are the conditions for total internal reflection?

Answer 7

▪ The ray of light should enter from a denser medium to a rarer
medium.
▪ The angle of incidence should be greater than the critical angle (ic )
for the given pair of media

Question 8

Define Critical Angle.

Answer 8

The angle of incidence in the denser medium, for which the angle of
refraction becomes 90º, is called the critical angle (ic ) for the given pair of
media.

Question 9

Write the relation connecting critical angle and refractive index

Answer 9

n=𝟏/𝐬𝐢𝐧 𝐢𝐜

Question 10

Define Power of a lens. Write its unit.
(D)

Answer 10

Power of a lens is the reciprocal of focal length expressed in metre
𝒑 =𝟏/𝒇
The SI unit for power of a lens is diopter

Question 10

.One diopter is the power of a lens of focal length …………………..

Answer 10

1m