Dual Nature Of Matter Question 7

Question 7 - 30 January - Shift 1

A small object at rest, absorbs a light pulse of power $20 mW$ and duration $300 ns$. Assuming speed of light as $3 \times 10^{8} m / s$. the momentum of the object becomes equal to :

(1) $0.5 \times 10^{-17} kg m / s$

(2) $2 \times 10^{-17} kg m / s$

(3) $3 \times 10^{-17} kg m / s$

(4) $1 \times 10^{-17} kg m / s$

Show Answer

Answer: (2)

Solution:

Formula: De Broglie wavelength

Momentum $=\frac{\text{ Energy }}{C}$

Power $\times$ time
$C$

$=\frac{(20 \times 10^{-3} w)(300 \times 10^{-9} s)}{3 \times 10^{8} m / s}$

$=2 \times 10^{-17} kg-m / s$