Answer :
The wavelength released during photoelectric effect is 353 nm.
We need to know about the photoelectric effect to solve this problem. The photoelectric effect is electron ejected from metal because of light source. The kinetic energy of the ejected electron is
K = (hc / λ) - (hc /λo)
where K is kinetic energy, h is Max Planck constant (6.6 x 10¯³⁴ Js), λ is the wavelength of light source and λo is the wavelength released from the metal.
From the question above, we know that
λ = 257 nm = 257 x 10¯⁹ m
c = 3 x 10⁸ m/s
v = 6.8 x 10⁵ m/s
me = 9.1 × 10¯³¹ kg
Find the wavelength released
K = hc . (1/λ - 1/λo)
1/2 . me .v² = 6.6 x 10¯³⁴ x 3 x 10⁸ . (1/257 x 10¯⁹ - 1/λo)
1/2 . 9.1 × 10¯³¹ . (6.8 x 10⁵)² = 6.6 x 10¯³⁴ x 3 x 10⁸ . (1/257 x 10¯⁹ - 1/λo)
2.10 x 10¯¹⁹ = 1.98 x 10¯²⁵ . (1/257 x 10¯⁹ - 1/λo)
2.10 x 10¯¹⁹ = (7.70 x 10¯¹⁹) - (1.98 x 10¯²⁵ / λo)
(1.98 x 10¯²⁵ / λo) = 5.60 x 10¯¹⁹
λo = 0.353 x 10¯⁶ m
λo = 353 nm
Find more on photoelectric effect at: https://brainly.com/question/1408276
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