Monochromatic light of wavelength 589 nm

cbse
waveoptics

#1

Monochromatic light of wavelength 589 nm is incident from air on a water surface. What are the wavelength, frequency and speed of
(i) reflected and
(ii) refracted light? (µ of water is 1.33).


#2

Here, wavelength λ = 589nm
c = 3 x ${{10}^{8}}$ m/s
µ = 1.33

(i) For reflected light,
Wavelength, λ = 589nm = 589 x ${{10}^{-9}}$ m
v = c/λ = 3 x ${{10}^{8}}$ / 589 x ${{10}^{-9}}$
= 5.09 x ${{10}^{14}}$ Hz
Speed, v=c=3 x ${{10}^{8}}$ m/s

(ii) For refracted light,
λ’ = λ/µ = 589 x ${{10}^{-9}}$/1.33 = 4.42 x ${{10}^{-7}}$ m

As frequency remains unaffected on entering another medium therefore

v’ = v = 5.09 x ${{10}^{14}}$ Hz

speed, v’ = c/µ = 3 x ${{10}^{8}}$/1.33
=2.25 x ${{10}^{8}}$ m/s