1 ) When a ray of light enters a glass slab from air
, its speed and wavelength , frequency ………..
Its speed and wavelength ……….. ( Decreases ) ,
but frequency ………….. ( Remains constant ) .
because glass is denser
medium and as we know that velocity of light in glass is lower than air . so by
that reason velocity decreases . And
velocity depends on refractive index of medium . Refractive index of medium is
inversely proportional to speed of light . Refractive index of glass is greater
than air . So speed of light decreases while
entering to glass slab from air medium . And speed of light will increase while entering to air medium from
glass slab .
We know a formula { v = f
λ } , as “ λ “ is wavelength , which is
directly related to velocity by this formula . So when velocity increases ,
then wavelength also increases and vice versa . So here according to question ,
wavelength will get decrease .
If we talk about
frequency , frequency works as a constant and frequency is also inherent property
of a wave . So frequency will remain same
every where either light enters denser medium or rare medium .
2
) For production of beats, two waves
must have ------------------- ,
A ) Same frequency , B ) Same
wavelength ,
C ) Same velocity , D ) None of
these ,
Correct
Answer : - A ) Same frequency ,
Beats are produced due to superposition of two waves which have slightly different frequencies
and have identical amplitudes.
3
) Beats is an application of
--------------------- ,
A ) Superposition , B
) Interference ,
C ) Both of these , D ) None of these ,
Correct
Answer : - A ) Superposition ,
Beats are produced due to propagation of superposition , not by interference . And it must have even
slightly different frequency .
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