Chp 4 unit B

Question 1

Define Prism

Answer 1

A prism is a transparent medium bounded by five plane surfaces with a triangular cross section

Question 2

Define angle of deviation. what is it denoted by?

Answer 2

the angle between the direction of incident ray and the emergent ray is called the angle of deviation. it is denoted by the greek letter delta.

Question 3

Define critical angle.

Answer 3

Critical angle is angle of incidence in the denser medium corresponding to which the angle of refraction in the rarer medium is 90 degrees.

Question 4

Factors affecting the critical angle

Answer 4

1) wavelength is directly proportional to Critical Angle. Red colour has the most critical angle and violet has the least Critical Angle.
2) temperature is directly proportional to Critical Angle.

Question 5

Define total internal reflection.

Answer 5

When are you of light travelling in a denser medium is incident at the surface of a rarer medium at an angle of incidence greater than the critical angle for the pair of media the ray is totally reflected back into the densher medium. This phenomenon is called total internal reflection.

Question 6

Conditions for total internal reflection.

Answer 6

1) the light must travel from a denser 2 is rare medium
2) the angle of incidence must be greater than the critical angle for the pair of media

Question 7

Distinction between total internal reflection and reflection from a plane mirror.

Answer 7

1) it takes place only when light passes from a dancer medium to a error medium and an angle of incidence greater than the critical angle for that pair of media.
It takes place when light is incident on a plane mirror from any medium at any angle of incidence.
2) the entire light is reflected.
a major part of light is reflected while the rest is refracted and absorbed.
3) there is no loss of energy. There is a loss of energy.
4) the image is much brighter and the brightness remains even after long use of the total reflecting device.
The image is less bright and the brightness gratuity decreases as the silvering on mirror becomes old and rock.

Question 8

Three consequences of total internal reflection

Answer 8

1) a crack in a glass vessel often shine like a mirror
2) a piece of diamond sparkles and viewed from certain directions.
3) an optical fibre is used to transmit a light signal over a long distance without any loss of energy.