Advertisements
Advertisements
Question
In an experiment on the photoelectric effect, the slope of the cut-off voltage versus the frequency of incident light is found to be 4.12 × 10−15 Vs. Calculate the value of Planck’s constant.
Advertisements
Solution
The slope of the cut-off voltage (V) versus frequency (v) of incident light is given as:
`V/v` = 4.12 × 10−15 Vs
V is related to frequency by the equation:
hv = eV
Where,
e = Charge on an electron = 1.6 × 10−19 C
h = Planck’s constant
∴ h = `e xx V/v`
= 1.6 × 10−19 × 4.12 × 10−15
= 6.592 × 10−34 Js
Therefore, the value of Planck’s constant is 6.592 × 10−34 Js.
APPEARS IN
RELATED QUESTIONS
Light of wavelength 488 nm is produced by an argon laser which is used in the photoelectric effect. When light from this spectral line is incident on the emitter, the stopping (cut-off) potential of photoelectrons is 0.38 V. Find the work function of the material from which the emitter is made.
In an accelerator experiment on high-energy collisions of electrons with positrons, a certain event is interpreted as annihilation of an electron-positron pair of total energy 10.2 BeV into two γ-rays of equal energy. What is the wavelength associated with each γ-ray? (1BeV = 109 eV)
Plot a graph showing the variation of photoelectric current with collector plate potential at a given frequency but for two different intensities I1 and I2, where I2 > I1.
Write Einstein’s photoelectric equation?
point out any two characteristic properties of photons on which Einstein’s photoelectric equation is based ?
Define the terms (i) ‘cut-off voltage’ and (ii) ‘threshold frequency’ in relation to the phenomenon of photoelectric effect.
Using Einstein’s photoelectric equation shows how the cut-off voltage and threshold frequency for a given photosensitive material can be determined with the help of a suitable plot/graph.
A non-monochromatic light is used in an experiment on photoelectric effect. The stopping potential
In a photoelectric experiment, the collector plate is at 2.0 V with respect to the emitter plate made of copper (φ = 4.5 eV). The emitter is illuminated by a source of monochromatic light of wavelength 200 nm. Find the minimum and maximum kinetic energy of the photoelectrons reaching the collector.
Use Einstein’s photoelectric equation to show how from this graph,
(i) Threshold frequency, and (ii) Planck’s constant can be determined.
Use Einstein's photoelectric equation to show how from this graph,
(i) Threshold frequency, and
(ii) Planck's constant can be determined.
Each photon has the same speed but different ______.
The wavelength of a photon needed to remove a proton from a nucleus which is bound to the nucleus with 1 MeV energy is nearly ______.
There are materials which absorb photons of shorter wavelength and emit photons of longer wavelength. Can there be stable substances which absorb photons of larger wavelength and emit light of shorter wavelength.
A student performs an experiment on photoelectric effect, using two materials A and B. A plot of Vstop vs ν is given in Figure.
- Which material A or B has a higher work function?
- Given the electric charge of an electron = 1.6 × 10–19 C, find the value of h obtained from the experiment for both A and B.
Comment on whether it is consistent with Einstein’s theory:
Radiation of frequency 1015 Hz is incident on three photosensitive surfaces A, B and C. Following observations are recorded:
Surface A: no photoemission occurs
Surface B: photoemission occurs but the photoelectrons have zero kinetic energy.
Surface C: photo emission occurs and photoelectrons have some kinetic energy.
Using Einstein’s photo-electric equation, explain the three observations.
A photon of wavelength 663 nm is incident on a metal surface. The work function of the metal is 1.50 eV. The maximum kinetic energy of the emitted photoelectrons is ______.
