Question
Define the terms threshold frequency and stopping potential in relation to the phenomenon of photoelectric effect. How is the photoelectric current affected on increasing the (1) frequency (2) intensity of the incident radiations and why?
✓
Answer
- Threshold frequency:
The minimum frequency of the incident radiation for a given metal below which emission of photo electrons does not take place.
- Stopping potential:
The minimum negative potential of the anode collector for which photoelectric current becomes zero.
- (1) (Practically) No effect/remain same.
As increase in frequency does not significantly change the number of photons in the beam.
(2) Increases:
The number of incident photons increases.
Need a full question paper?
Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.
Explore more
Similar questions
- Describe the working of photodiode by drawing the circuit diagram.
- Draw the characteristics of a photodiode for different illumination intensities.
- Why is photodiode operated in reverse bias even though the reverse bias current is much weaker than the current in forward bias?
A nearsighted person cannot see beyond 25cm. Assuming that the separation of them glass from the eye is 1cm, find the power of lens needed to see distant objects.
(i) Write the name of device 'Y' in the following given diagram
(ii) Draw the circuit diagram of device 'Y'.
(iii) If the frequency of input signal is 60 Hz than what is the frequency of the output signal in a full wave rectifier?
(ii) Draw the circuit diagram of device 'Y'.
(iii) If the frequency of input signal is 60 Hz than what is the frequency of the output signal in a full wave rectifier?
The variation of intensity of magnetisation I and the applied magnetic field intensity H for three magnetic materials X, Y and Z are as shown in the given graphs.
- Identify the materials X, Y and Z.
- Show graphically the variation of susceptibility with temperature for X.
- Put of Y and Z, which of the material will you prefer for making transformer cores and why?
The average separation between the proton and the electron in a hydrogen atom in ground state is 5.3 × 10-11 m.
- Calculate the Coulomb force between them at this separation.
- When the atom goes into its first excited state the average separation between the proton and the electron increases to four times its value in the ground state.What is the Coulomb force in this state?
The current through a wire depends on time as $\text{i}=\text{i}_0+\alpha\text{t},$
Where $\text{i}_0=10\text{A}$ and $\alpha=4\text{A/ s}.$ Find the charge that crosses through a section of the wire in 10 seconds.
→Where $\text{i}_0=10\text{A}$ and $\alpha=4\text{A/ s}.$ Find the charge that crosses through a section of the wire in 10 seconds.
A spacecraft consumes more fuel in going from the earth to the moon than it takes for a return trip. Comment on this statement.
A semiconducting material has a band gap of 1eV. Acceptor impurities are doped into it which create acceptor levels 1meV above the valence band. Assume that the transition from one energy level to the other is almost forbidden if kT is less than $\frac{1}{50}$ of the energy gap. Also, if kT is more than twice the gap, the upper levels have maximum population. The temperature of the semiconductor is increased from 0K. The concentration of the holes increases with temperature and after a certain temperature it becomes approximately constant. As the temperature is further increased, the hole concentration again starts increasing at a certain temperature. Find the order of the temperature range in which the hole concentration remains approximately constant.
→Three capacitors of capacitances 2 pF, 3 pF and 4 pF are connected in parallel.
- What is the total capacitance of the combination?
- Determine the charge on each capacitor if the combination is connected to a 100 V supply.
Characteristic X-rays may be used to identify the element from which they are being emitted. Can continuous X-rays be used for this purpose?