Radiation, with wavelength 6561 Å falls on a metal surface to produce photoelectrons. The electrons are made to enter a uniform magnetic field of 3 × 10 - 4 T . If the radius of the largest circular path followed by the electrons is 10 m m , the work function of the metal is close to:

K E m a x = E - ϕ = 12400 λ i n Å - ϕ (in eV) ∴ r = 2 m K E e B K E m a x = r 2 e 2 B 2 2 m (in J) = r 2 e B 2 2 m (in eV) ∴ ϕ = 12400 6556 - r 2 e B 2 2 m = 1.1 e V

Physics - Magnetism Question with Solution | TestHub

PhysicsMagnetismMagnetic ForceMedium2 minPYQ_2020

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Radiation, with wavelength $6561 Å$ falls on a metal surface to produce photoelectrons. The electrons are made to enter a uniform magnetic field of $3 \times 10^{- 4} T$ . If the radius of the largest circular path followed by the electrons is $10 m m$ , the work function of the metal is close to:

Options:

Answer:

Solution:

$K E_{m a x} = E - ϕ$
$= \frac{12400}{λ (i n Å)} - ϕ$ (in eV)
$∴ r = \frac{\sqrt{2 m K E}}{e B}$
$K E_{m a x} = \frac{r^{2} e^{2} B^{2}}{2 m}$ (in J)
$= \frac{r^{2} e B^{2}}{2 m}$ (in eV)
$∴ ϕ = \frac{12400}{6556} - \frac{r^{2} e B^{2}}{2 m}$
$= 1.1 e V$

Stream:JEESubject:PhysicsTopic:MagnetismSubtopic:Magnetic Force

⏱ 2mℹ️ Source: PYQ_2020

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