The work function of a metal is 1.6 × 10-19 J. When the metal surface is illuminated by the light of wavelength 6400 mathringA, then the maximum kinetic energy of emitted photo-electrons will be (Planck's constant .h=6.4 × 10-34 Js )

Question

The work function of a metal is 1.6 × 10-19 J. When the metal surface is illuminated by the light of wavelength 6400 mathringA, then the maximum kinetic energy of emitted photo-electrons will be (Planck's constant .h=6.4 × 10-34 Js ) (A) 14 × 10-19 J (B) 2.8 × 10-19 J (C) 1.4 × 10-19 J (D) 1.4 × 1019 J

Tardigrade Admin · Accepted Answer

K max =(h c/λ)-W0 =(6.4 × 10-34 × 3 × 108/6400 × 10-10)-1.6 × 10-19 =1.4 × 10-19 J

Q. The work function of a metal is $1.6 \times 1 0^{- 19} J$ . When the metal surface is illuminated by the light of wavelength $6400 \overset{˚}{A}$ , then the maximum kinetic energy of emitted photo-electrons will be
(Planck's constant $h = 6.4 \times 1 0^{- 34} J s)$

$14 \times 1 0^{- 19} J$

$2.8 \times 1 0^{- 19} J$

$1.4 \times 1 0^{- 19} J$

$1.4 \times 1 0^{19} J$

$K_{m a x} = \frac{h c}{λ} - W_{0}$
$= \frac{6.4 \times 1 0 ^{- 34} \times 3 \times 1 0 ^{8}}{6400 \times 1 0 ^{- 10}} - 1.6 \times 1 0^{- 19}$
$= 1.4 \times 1 0^{- 19} J$

Q. The work function of a metal is 1.6×10−19J. When the metal surface is illuminated by the light of wavelength 6400A˚, then the maximum kinetic energy of emitted photo-electrons will be (Planck's constant h=6.4×10−34Js)

14×10−19J

2.8×10−19J

1.4×10−19J

1.4×1019J