Answer:
a) f = (1.24 × 10^15) Hz and E = (8.214 × 10^-19) J
b) f = (1.36 × 10^15) Hz; E = (9.035 × 10^-19) J
Explanation:
a) The least energetic photons have the highest wavelength. That is, the wavelength of the least energetic photons is equal to the upperlimit of the wavelength inequality given.
λ = 242nm = 2.42 × 10⁻7 m
v = fλ; f = v/λ; v = 3×10^8 m/s
f = (3×10^8)/(2.42×10^-7)
f = (1.24 × 10^15) Hz
E = hf; h = planck's constant = (6.62607004 × 10^-34) Js
E = 6.626 × 10^-34 × 1.24 × 10^15
E = (8.214 × 10^-19) J
b) The photons with the least wavelength in the range provided are the most energetic ones.
λ = (2200 × 10^-10) m = (2.2 × 10^-7) m
v = fλ; f = v/λ; v = 3×10^8 m/s
f = (3×10^8)/(2.2×10^-7)
f = (1.36 × 10^15) Hz
E = hf; h = planck's constant = (6.62607004 × 10^-34) Js
E = 6.626 × 10^-34 × 1.36 × 10^15
E = (9.035 × 10^-19) J
QED!