Download App

Electron, Photon, Photo-electric Effect and X-Rays — JEE physics STD 12 Science — Question

CBSE BoardEnglish MediumSTD 12 ScienceJEE physicsElectron, Photon, Photo-electric Effect and X-Rays1 Mark
MCQ
Mercury violet light $(\lambda=4558\  \mathring A)$ is falling on a photosensitive material $(\phi=2.5 \mathrm{eV})$. The speed of the ejected electrons is in $m s^{-1}$, about
  • A
    $3 \times 10^5$
  • ✓
    $2.65 \times 10^5$
  • C
    $4 \times 10^4$
  • D
    $3.65 \times 10^7$
✓

Answer

Correct option: B.
$2.65 \times 10^5$
$ \text { By using } E=W_0+\frac{1}{2} m v_{\max }^2 ; \text { where } E=\frac{12375}{4558}=2.71 \mathrm{eV} $
$ \Rightarrow 2.71 \mathrm{eV}=2.5 \mathrm{eV}+\frac{1}{2} \times 9.1 \times 10^{-31} \times v_{\max }^2 $
$ \Rightarrow 0.21 \times 1.6 \times 10^{-19}=\frac{1}{2} \times 9.1 \times 10^{-31} \times v_{\max }^2 $
$ \Rightarrow v_{\max }=2.65 \times 10^5 \mathrm{~m} / \mathrm{s}$

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free

Explore more

More "MCQ" from Electron, Photon, Photo-electric Effect and X-Rays→Electron, Photon, Photo-electric Effect and X-Rays — all question types→JEE physics STD 12 Science question papers→CBSE Board STD 12 Science question papers→CBSE Board question paper generator→

Similar questions

The angle between the vectors $(\hat{i} \quad \hat{j})$ and $(\hat{j} \quad \hat{k})$ is
→
The speed of electromagnetic wave in vacuum depends upon the source of radiation
→
The waves in which the particles of the medium vibrate in a direction perpendicular to the direction of wave motion is known as
→
The threshold wavelength for photoelectric effect of a metal is $6500\ \mathring A$. The work function of the metal is approximately
→
When an electron in hydrogen atom is excited, from its $4^{\text {t to }} 5^*$ stationary orbit, the change in angular momentum of electron is (Planck's constant: $h=6.6 \times 10^{-34} J - s$ )
→
In a $P N$-junction
→
The magnetic lines of force inside a bar magnet
→
Which of the following is not correct regarding the radio telescope
→
A body is moving in a room with a velocity of $20 m / s$ perpendicular to the two walls separated by 5 meters. There is no friction and the collisions with the walls are elastic. The motion of the body is
→
On a glass plate a light wave is incident at an angle of $60^{\circ}$. If the reflected and the refracted waves are mutually perpendicular, the refractive index of material is
→