Light of wavelength ' $\lambda$ ' which is less than threshold wavelength is incident on a photosensitive material. If incident wavelength is decreased so that emitted photoelectrons are moving with same velocity then stopping potential willA) increaseB) decreaseC) be zeroD) become exactly half

Home » Light of wavelength ‘ ‘ which is less than threshold wavelength is incident on a photosensitive material. If incident wavelength is decreased so that emitted photoelectrons are moving with same velocity then stopping potential willA) increaseB) decreaseC) be zeroD) become exactly half

Light of wavelength ‘ $\lambda$ ‘ which is less than threshold wavelength is incident on a photosensitive material. If incident wavelength is decreased so that emitted photoelectrons are moving with same velocity then stopping potential will
A) increase
B) decrease
C) be zero
D) become exactly half

Physics

Light of wavelength ‘ $\lambda$ ‘ which is less than threshold wavelength is incident on a photosensitive material. If incident wavelength is decreased so that emitted photoelectrons are moving with same velocity then stopping potential will
A) increase
B) decrease
C) be zero
D) become exactly half

Answer is (A)
According to photoelectric equation,
$\frac{\mathrm{hc}}{\lambda}-\phi=\mathrm{E} \quad$ where $\mathrm{E}=\frac{\mathrm{p}^{2}}{2 \mathrm{~m}}(\mathrm{~K} . \mathrm{E})$
If $E$ is constant $\Rightarrow$ then $\frac{1}{\lambda} \propto \phi$
If we decrease the wavelength $\lambda$ , then stopping potential $\phi$ will increase such that $\frac{\text { hc }}{\lambda}-\phi=$ constant.

i

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