dual nature

Question 1

What are the different mehods of electron emission from a metal surface

Answer 1

Thermionic emission
Field Emission
Photo-electric emission

Question 2

What is photoelectric Effect

Answer 2

The phenomenon of emission of electrons when photosensitive substances
are illuminated by light of suitable frequency is called photoelectric effect.
i.e., the photocurrent increases linearly with intensity of incident light.

Question 3

Define work function

Answer 3

The minimum energy required by an electron to escape from a metal
surface is called work function
𝜙0 = h𝑣0 (where 𝑣0 is threshold frequency)
work function is expressed in electron volt(eV)

Question 4

Define threshold frequency

Answer 4

The minimum frequency of incident radiation below which photo electric
emission is not possible is called threshold frequency(𝑣0).
𝒗𝟎=𝝓𝟎/𝒉

Greater the work function ,greater the threshold frequency.

Question 5

Define stopping potential

Answer 5

The stopping potential is the minimum negative potential applied to the
anode at which the photo emission stops.

Question 6

The work function of a metal is 6eV. If two photons each having energy 4
eV strike the metal surface. Will the emission be possible? Why?

Answer 6

No, photo emission is not possible.
Photo emission is possible only if ℎ𝑣 > 𝜙0

Here energy of incident photon is less than work function
and hence photo emission is not possible

Question 7

Draw a graph showing the variation of photocurrent with intensity of
light.

Answer 7

When intensity of incident radiation is increased the number of
photoelectrons emitted per second increases and hence the photoelectric
current also increases.

Question 8

Why macroscopic objects in our daily life do not show wave-like
properties?

Answer 8

The wavelength associated with macroscopic objects is so small that it is
beyond any measurement. So macroscopic objects in our daily life do not
show wave-like properties.

Question 8

Write the properties of photon

Answer 8

1) In the interaction of light with matter , light behaves as if it is made
up of particles called photon.
2) Each photon has energy, E=hν and momentum p= hν/c and
Speed c= 3x 108m/s
3)All photons of light of a particular frequency ν, or wavelength λ, have
the same energy and momentum p, whatever the intensity of
radiation may be.
4) When intensity of light is increased only the number of photons
increases, but the energy of photon is independent of intensity of light.
5) Photons are electrically neutral. They are not deflected by electric
and magnetic fields.
6) In photon-particle collision total energy and total momentum are
conserved. However, the number of photons may not be conserved in a
collision. The photon may be absorbed or a new photon may be created.