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Question : 7
Total: 8
Answer the following:
(a) Name the e.m. waves which are used for the treatment of certain forms of cancer. Write their frequency range.
(b) Thin ozone layer on top of stratosphere is crucial for human survival. Why?
(c) Why is the amount of the momentum transferred by the e.m. waves incident on the surface so small?
(a) Name the e.m. waves which are used for the treatment of certain forms of cancer. Write their frequency range.
(b) Thin ozone layer on top of stratosphere is crucial for human survival. Why?
(c) Why is the amount of the momentum transferred by the e.m. waves incident on the surface so small?
Solution:
(a) Gamma rays are used for the treatment of certain forms of cancer. Their frequency range is 3 × 10 19 Hz 5 × 10 20 Hz
(b) The thin ozone layer on top of stratosphere absorb most of the harmful ultraviolet rays coming from the Sun towards the Earth. They include UVA, UVB and UVC radiations, which can destroy the life system on the Earth. Hence, this layer is crucial for human survival.
(c) The momentum transported by electromagnetic waves is given by
p =
=
whereU c
Now,h = 6.62 × 10 − 34 J s , c = 3 × 10 8 m s − 1
Therefore, even forγ ( v ≈ 10 20 Hz )
p =
= 2.2 × 10 − 22 kg m s − 1
Thus, the amount of the momentum transferred by the e.m. waves incident on a surface is very small.
(b) The thin ozone layer on top of stratosphere absorb most of the harmful ultraviolet rays coming from the Sun towards the Earth. They include UVA, UVB and UVC radiations, which can destroy the life system on the Earth. Hence, this layer is crucial for human survival.
(c) The momentum transported by electromagnetic waves is given by
where
Now,
Therefore, even for
Thus, the amount of the momentum transferred by the e.m. waves incident on a surface is very small.
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