Question

A small metal plate (work function =1.17 eV) is placed at a distance of 2m from a monochromatic source of light of wavelength 4.8×m and power 20​

Answer 1

ANSWER:

For a light source of say 20 watt the number of photons if n and each having nu frequency

E = n.h. nu

where E is total energy and nu = c/lambda = 3.10^8 /(4.8 .10^-7) per sec

so photon number n per sec = E/(h . nu)

therefore per square meter

this photon flux = (1/4 pi) (E/h.nu) per sq m per sec

but the plate is at 2m therefore the flux will further decrease to 1/4 using inverse square law

= (1/16 pi) (E/h.nu) per sq m per sec

= (1/16 pi) {20 J /s }/ {6.62 . 10^-34 J-s x (5/8 ) 10^15}

so

the number of photons

hitting the plate per square meter = approx 10^20 photons /sq m-sec

SORRY GUYS ..BOOK KE HELPS SE ANSWER DE RAHA HU.....