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# If a source of power $4\: kW$ produce $10^{20}$photons/s, the radiation belongs to a part of spectrum called

$\begin {array} {1 1} (a)\;X-rays & \quad (b)\;ultraviolet\: rays \\ (c)\;microwaves & \quad (d)\;\gamma - rays \end {array}$

Can you answer this question?

$4 \times 10^3 = 10^{20} \times h\nu$
where, $\nu =$ frequency
$\Rightarrow \nu =\large\frac{ 4 \times 10^3 }{(10^{20} \times 6.023 \times 10^{-34} )}$
$\Rightarrow \nu = 6.64 \times 10^{16}Hz$
This frequency lies in the band of x-rays.
Ans : (a)

answered Feb 28, 2014
edited Oct 3, 2014