NEET Class neet Answered

? Help me in (b) and (c) ... Explnation needed...!! Thanq

Asked by jhajuhi19 | 22 Apr, 2020, 08:32: AM

Expert Answer

Work function of Caesium is,

Φ₀ = 2.14 eV

a) Maximum wavelength that can cause photoelectric effect is called threshold wavelength of incident radiation.

Thus, threshold wavelength of Caesium is given by,

Error converting from MathML to accessible text.

b) The wavelength of incident light if photoelectron is brought to zero by retarding potential also known as stopping potential of 0.60 V

W e space k n o w comma space m a x i m u m space k i n e t i c space e n e r g y space o f space p h o t o space e l e c t r o n s space i n space t e r m s space o f space s t o p p i n g space p o t e n t i a l space i s space g i v e n space a s comma space K. E subscript m a x end subscript space equals space left parenthesis open vertical bar V subscript 0 close vertical bar right parenthesis e V space space equals 0.60 space e V space equals space space 0.60 space cross times 1.6 cross times 10 to the power of negative 19 end exponent space J space space.... space left parenthesis asterisk times right parenthesis space e V subscript 0 space equals space fraction numerator h c over denominator lambda end fraction space minus space ϕ subscript 0 space rightwards double arrow lambda space equals space fraction numerator h c over denominator e V subscript 0 space plus space ϕ subscript 0 space end fraction space equals space fraction numerator 6.63 space cross times 10 to the power of negative 34 end exponent cross times 3 cross times 10 to the power of 8 over denominator left parenthesis 0.6 plus 2.14 right parenthesis cross times 1.6 cross times 10 to the power of negative 19 end exponent end fraction space equals 4530 space A with omicron on top space

c) Maximum speed of electrons emitted in case of (b)

W e space k n o w comma space 1 half m v subscript m a x end subscript superscript 2 space equals space K. E subscript m a x end subscript F r o m space e q u a t i o n space left parenthesis asterisk times right parenthesis comma space space K. E subscript m a x end subscript space equals space 0.6 space cross times 1.6 cross times 10 to the power of negative 19 end exponent space J space T h u s comma space 1 half left parenthesis 9.1 space cross times 10 to the power of negative 31 end exponent right parenthesis space cross times space v subscript m a x end subscript superscript 2 space equals space space 0.6 space cross times 1.6 cross times 10 to the power of negative 19 end exponent space space v subscript m a x end subscript superscript 2 space equals space fraction numerator 0.6 space cross times 1.6 cross times 10 to the power of negative 19 end exponent space space cross times 2 over denominator 9.1 space cross times 10 to the power of negative 31 end exponent end fraction space equals space 0.210 space cross times space 10 to the power of 12 space therefore space v subscript m a x end subscript space equals space square root of 0.210 space cross times space 10 to the power of 12 end root space equals space 0.458 space cross times 10 to the power of 6 space equals space 4.58 space cross times 10 to the power of 5 space m divided by s space space

Thus, maximum speed of electrons emitted is 4.58×10⁵ m/s

Answered by Shiwani Sawant | 22 Apr, 2020, 14:51: PM

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