Physics
The critical angle for glass-air is 45° for the light of yellow colour. State whether it will be less than, equal to, or more than 45° for
(i) red light,
(ii) blue light ?
Answer
As the wavelength of light decreases (or increases) refractive index becomes more (or less) and critical angle becomes less (or more).
(i) As the wavelength for red light is more than that for yellow colour, the refractive index becomes less and the critical angle will be more than 45°.
(ii) As the wavelength for blue light is less than that for yellow colour, the refractive index becomes more and the critical angle will be less than 45°.
Related Questions
A ray of white light is incident on the interface of glass and air as shown in the figure. At the given angle of incidence, green light suffers total internal reflection. The rays emerging out from glass to air contain :
- yellow, orange and red colours
- violet, indigo and blue colours
- all colours
- all colours except green
How is the critical angle related to the refractive index of a medium?
Which colour of light has higher critical angle ? Red light or green light.
Fill in the blanks to complete the following sentences —
(a) Total internal reflection occurs only when a ray of light passes from a ………. medium to a ………. medium.
(b) Critical angle is the angle of ………. in denser medium for which the angle of ………. in rarer medium is ……….