Values of work function ( W 0 ) for a few metals are given below Metal Li Na K Mg Cu Ag W 0 eV 2 . 42 2 . 3 2 . 25 3 . 7 4 . 8 4 . 3 The number of metals which will show photoelectric effect when light of wavelength 400 nm falls on it is _____ Given: h = 6 . 6 × 10 – 34 J s c = 3 × 10 8 ms – 1 e = 1 . 6 × 10 – 19 C

Question

Values of work function ( W 0 ) for a few metals are given below Metal Li Na K Mg Cu Ag W 0 eV 2 . 42 2 . 3 2 . 25 3 . 7 4 . 8 4 . 3 The number of metals which will show photoelectric effect when light of wavelength 400 nm falls on it is _____ Given: h = 6 . 6 × 10 – 34 J s c = 3 × 10 8 ms – 1 e = 1 . 6 × 10 – 19 C,

MARKS App · Accepted Answer

The minimum amount of energy necessary to start the emission of electrons from a metal's surface is known as its work function. The work function is the minimum amount of energy required to remove an electron from a metal's surface to infinity. Energy of incident photon = h c λ = 6 . 6 × 10 - 34 × 3 × 10 8 400 × 10 - 9 J = 6 . 6 × 10 - 34 × 3 × 10 8 400 × 10 - 9 × 1 . 6 × 10 - 9 eV = 3 . 1 eV If radiation energy is greater than work function of metal, then metal show photo electric effect. ∴ Li , Na and K will show photoelectric effect.

Metal	$Li$	$Na$	$K$	$Mg$	$Cu$	$Ag$
$\frac{W_{0}}{eV}$	$2.42$	$2.3$	$2.25$	$3.7$	$4.8$	$4.3$

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