Download App

Dual Nature of Radiation and Matter — Physics STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 SciencePhysicsDual Nature of Radiation and Matter3 Marks
Question
Define the term work function of a metal. The threshold frequency of a metal is $2 f_0$. When the light of frequency $2 f_0$ is incident on the metal plate, the maximum velocity of electrons emitted is $\mathrm{v}_1$ When the frequency of the incident radiation is increased to $5 f_0$ the maximum velocity of electrons emitted is $v_2$. Find the ratio of $v_1$ to $v_2$.
✓

Answer

Work function: The work function of a metal is defined as the minimum energy required to free an electron from its surface binding. Einstein's photoelectric equation is $h \nu=h \nu_0+\frac{1}{2} m v^2$ In first case $V=2 f_0, V_0=f_0, v=v_1$ $\mathrm{h}\left(2 \mathrm{f}_0\right)=\mathrm{hf}_0+\frac{1}{2} \mathrm{mv}_1^2 \Rightarrow \frac{1}{2} \mathrm{mv}_1^2=\mathrm{hf}_0$
In second case, $v=5 f_0, V_0=f_0, v=v_2$
$\therefore \mathrm{h}\left(5 \mathrm{f}_0\right)=\mathrm{hf}_0+\frac{1}{2} \mathrm{mv}_2^2 \Rightarrow \frac{1}{2} \mathrm{mv}_2^2=4 \mathrm{hf}_0$ Dividing $\left(\frac{v_1}{v_2}\right)^2=\frac{1}{4} \Rightarrow \frac{v_1}{v_2}=\frac{1}{2}$.

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 "3 Marks Question" from Dual Nature of Radiation and Matter→Dual Nature of Radiation and Matter — all question types→Physics STD 12 Science question papers→Gujarat Board STD 12 Science question papers→Gujarat Board question paper generator→

Similar questions

A monochromatic light source of intensity 6mW emits $8 \times 10^{16} $ photons per second. This light ejects photoelectrons from a metal surface. The stopping potential for this setup is 2.0V. Calculate the work function of the metal.
→
A coil of resistance $100\Omega$ is connected across a battery of emf 6.0V. Assume that the heat developed in the coil is used to raise its temperature. If the heat capacity of the coil is 4.0J/K, how long will it take to raise the temperature of the coil by 15^^\circC?
→
A metal wire PQ of mass 10g lies at rest on two horizontal metal rails separated by 4.90cm A vertically-downward magnetic field of magnitude 0.800T exists in the space. The resistance of the circuit is slowly decreased and it is found that when the resistance goes below 20.0Ω, the wire PQ starts sliding on the rails. Find the coefficient of friction.
→
Find the energy, the frequency and the momentum of an X-ray photon of wavelength 0.10nm.
→
A railway track (made of iron) is laid in winter when the average temperature is 18°C. The track consists of sections of 12.0m placed one after the other. How much pp should be left between two such sections 80 that there is no compression during summer when the maximum temperature goes to 48°C? Coefficient of linear expansion of iron ${= 11 \times 10^{-6}}^\circ C^{-1}.$
→
Indium antimonide has a band gap of 0.23eV between the valence and the conduction band. Find the temperature at which kT equals the band gap.
→
A change of 0.2mA in the base current causes a change of 5mA in the collector current for a common emitter amplifier.
  1. Find the ac current gain of the transistor.
  2. If the input resistance is $2\text{k}\Omega$ and its voltage gain is 75, calculate the load resistor used in the circuit.
→
An ideal battery sends a current of 5A in a resistor. When another resistor of value $10\Omega$ is connected in parallel, the current through the battery is increased to 6A. Find the resistance of the first resistor.
→
Define the term 'resolving power' of an astronomical telescope. How does it get affected on?
  1. Increasing the aperture of the objective lens?
  2. Increasing the wavelength of the light used?
Justify your answer in each case.
→
A solid sphere is set into motion on a rough horizontal surface with a linear speed v in the forward direction and an angular speed $\frac{\text{v}}{\text{R}}$ in the anticlockwise direction as shown in figure. Find the linear speed of the sphere:
  1. When it stops rotating.
  2. When slipping finally ceases and pure rolling starts.
→