Question

What is the frequency of a helium-neon laser light with a wavelength of $ 632.8nm $ ? The speed of light is $ 3.00 \times 10^8 ms^ { -1 } $ .

Answer 1

Hint: To solve the given question, we should have knowledge about frequency, wavelength and speed of light.
Frequency is known as the number of oscillations of waves per unit time. It is expressed in $ Hertz $ . Wavelength is the distance crests and troughs. It is mainly expressed in $ m $ .
Speed of light basically is the speed of light particles travelling in vacuum. Its value is $ 3 \times 10^8 msec^ { -1 } $ .
The only formula used is :
 $ v =\nu \lambda $
where,
 $ v \rightarrow $ Speed of light
 $ \nu \rightarrow $ Frequency of laser light
 $ \lambda \rightarrow $ Wavelength of laser light.

Complete step by step solution:
Step-1 :
We have given the speed of light as $ 3 \times 10^8 msec^ { -1 } $ and the wavelength helium-neon laser light is $ 632.8 nm $ , which can be further equal to $ 632.8 \times 10^ { -9 } $ .
Step-2 :
Using the given above formula, we have ;
 $ \nu = \dfrac { v } { \lambda } $
 $ = \dfrac { 3 \times 10^8 }{ 632.8 \times 10^ { -9} } $
 $ = 4.7 \times 10^{ 14 } Hz $

Note:
We know that frequency is always calculated in $ Hertz $ and for that the rest of the values must be in $ SI $ units too. In case of laser light, laser refers to light amplification by stimulated emission of radiation. Lasers can have a speed greater than that of light.