Q140 / 150 · MHT CET 2026 (15 April Shift 1) · 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 some velocity then stopping potential
- Abecomes half
- Correct answerBincreases
- Cdecreases
- Dis zero
Solution
According to Einstein's photoelectric equation, the maximum kinetic energy of emitted photoelectrons is given by
$K_{\max} = \dfrac{hc}{\lambda} - \Phi$
where $\lambda$ is the incident wavelength and $\Phi$ is the work function of the material.
The stopping potential $V_s$ is related to the maximum kinetic energy by
$eV_s = K_{\max} = \dfrac{hc}{\lambda} - \Phi$
When the incident wavelength $\lambda$ is decreased, the term $\dfrac{hc}{\lambda}$ increases. Since the work function $\Phi$ remains constant for a given material, the maximum kinetic energy $K_{\max}$ of the photoelectrons increases.
Consequently, the stopping potential $V_s$ also increases.
Answer: increases
$K_{\max} = \dfrac{hc}{\lambda} - \Phi$
where $\lambda$ is the incident wavelength and $\Phi$ is the work function of the material.
The stopping potential $V_s$ is related to the maximum kinetic energy by
$eV_s = K_{\max} = \dfrac{hc}{\lambda} - \Phi$
When the incident wavelength $\lambda$ is decreased, the term $\dfrac{hc}{\lambda}$ increases. Since the work function $\Phi$ remains constant for a given material, the maximum kinetic energy $K_{\max}$ of the photoelectrons increases.
Consequently, the stopping potential $V_s$ also increases.
Answer: increases
Hence, the correct answer is option: 'B'.