Browse Questions

Some radio waves of frequency of about $1.5 \times 10^9\: Hz$ was received by a radio-telescope from distant star. If the speed of the waves is $3 \times 10^5\: km/s$ , then the wave- length of the wave will be:

$\begin {array} {1 1} (a)\;0.1\: m & \quad (b)\;0.6\: m \\ (c)\;0.2\: m & \quad (d)\;0.46\: m \end {array}$

$v = 1.5 \times 10^9\: Hz$
$c = 3 \times 10^5\: km/s = 3 \times 10^8\: m/s$
So, $\lambda = \large\frac{c}{v}$ $= \large\frac{3 \times 10^8 }{(1.5 \times 10^9 ) }$$= 0.2\: m$
Ans : (c)