A 1.5 kW laser beam of wavelength 6400 mathringA is used to levitate a thin aluminium disc of same are a as the cross-section of the beam. The laser light is reflected by the aluminium disc without any absorption. The mass of the foil is close to

Question

A 1.5 kW laser beam of wavelength 6400 mathringA is used to levitate a thin aluminium disc of same are a as the cross-section of the beam. The laser light is reflected by the aluminium disc without any absorption. The mass of the foil is close to (A) 10-9 kg (B) 10-3 kg (C) 10-4 kg (D) 10-6 kg

Tardigrade Admin · Accepted Answer

Force due to radiation pressure = Weight of disc ⇒ (2p/c) =mg ⇒ (2×1.5×103/3×108)=m×10 ⇒ m=10-6 Kg

Q. A $1.5 kW$ laser beam of wavelength $6400 \overset{˚}{A}$ is used to levitate a thin aluminium disc of same are a as the cross-section of the beam. The laser light is reflected by the aluminium disc without any absorption. The mass of the foil is close to

$1 0^{- 9} k g$

$1 0^{- 3} k g$

$1 0^{- 4} k g$

$1 0^{- 6} k g$

Force due to radiation pressure $=$ Weight of disc
$\Rightarrow \frac{2 p}{c} = m g$
$\Rightarrow \frac{2 \times 1.5 \times 1 0 ^{3}}{3 \times 1 0 ^{8}} = m \times 10$
$\Rightarrow m = 1 0^{- 6} K g$

Q. A 1.5kW laser beam of wavelength 6400A˚ is used to levitate a thin aluminium disc of same are a as the cross-section of the beam. The laser light is reflected by the aluminium disc without any absorption. The mass of the foil is close to

10−9kg

10−3kg

10−4kg

10−6kg