A small plate of area 1 cm² is placed at a distance 1/π m from an isotropic point source emitting light of frequency (1/6.63) × 10¹⁴ Hz at a power of 2.00 mW. The plate is normal to the incident radiation. Take h = 6.63 × 10⁻³⁴ J s. Select the correct statements.
Select all that apply

Question

A small plate of area 1 cm² is placed at a distance 1/π m from an isotropic point source emitting light of frequency (1/6.63) × 10¹⁴ Hz at a power of 2.00 mW. The plate is normal to the incident radiation. Take h = 6.63 × 10⁻³⁴ J s. Select the correct statements.

Select all that apply

G1 Physics · Accepted Answer

Photon energy is Eγ = hν = 10⁻²⁰ J, so the source emits P/Eγ = 2.0 × 10⁻³/10⁻²⁰ = 2 × 10¹⁷ photons s⁻¹. The plate intercepts the geometric fraction A/(4πr²) of the isotropic beam; using the printed area and distance gives the stated intercepted fraction and photon-hit rate. Thus all four listed statements are correct. Correct answer: A, B, C, D.