NEET Dual Nature of Matter — Set 8

Question 1

What happens to photoelectric emission if the frequency of incident light is below the threshold frequency?

Accepted Answer

No photoelectric emission occurs if the frequency is below the threshold frequency, as the photon energy ($ h v $) is less than the work function ($ \phi_0 $).

Question 2

The de Broglie wavelength of a particle of mass $ 5.0 \times 10^{-30} \, \text{kg} $ moving at $ 2.0 \times 10^5 \, \text{m/s} $ is:

Accepted Answer

Momentum $ p = m v = 5.0 \times 10^{-30} \times 2.0 \times 10^5 = 1.0 \times 10^{-24} \, \text{kg m/s} $. $ \lambda = \frac{h}{p} = \frac{6.63 \times 10^{-34}}{1.0 \times 10^{-24}} = 6.63 \times 10^{-10} \, \text{m} = 0.663 \, \text{nm} $.

Question 3

The de Broglie wavelength of an electron is $ 0.2 \, \text{nm} $. What is its speed? (Take $ h = 6.63 \times 10^{-34} \, \text{J s} $, $ m_e = 9.11 \times 10^{-31} \, \text{kg} $)

Accepted Answer

$ p = \frac{h}{\lambda} = \frac{6.63 \times 10^{-34}}{0.2 \times 10^{-9}} = 3.315 \times 10^{-24} \, \text{kg m/s} $. $ v = \frac{p}{m} = \frac{3.315 \times 10^{-24}}{9.11 \times 10^{-31}} \approx 3.64 \times 10^6 \, \text{m/s} $.

NEET Physics: Dual Nature of Matter — Practice Set 8

Q1. What happens to photoelectric emission if the frequency of incident light is below the threshold frequency?

Q2. The de Broglie wavelength of a particle of mass \( 5.0 \times 10^{-30} \, \text{kg} \) moving at \( 2.0 \times 10^5 \, \text{m/s} \) is:

Q3. The de Broglie wavelength of an electron is \( 0.2 \, \text{nm} \). What is its speed? (Take \( h = 6.63 \times 10^{-34} \, \text{J s} \), \( m_e = 9.11 \times 10^{-31} \, \text{kg} \))

Q4. The momentum of a photon is \( 2.21 \times 10^{-27} \, \text{kg m/s} \). What is its wavelength? (Take \( h = 6.63 \times 10^{-34} \, \text{J s} \))

Q5. Which scientist proposed that moving particles of matter exhibit wave-like properties?

Q6. The threshold frequency of a metal is \( 4.8 \times 10^{14} \, \text{Hz} \). What is the maximum kinetic energy for light of frequency \( 6.8 \times 10^{14} \, \text{Hz} \)? (Take \( h = 6.63 \times 10^{-34} \, \text{J s} \))

Q7. The threshold wavelength for a metal is \( 600 \, \text{nm} \). What is its work function in eV? (Take \( h c = 1240 \, \text{eV nm} \))

Q8. Light of wavelength \( 450 \, \text{nm} \) is incident on a metal with work function \( 1.9 \, \text{eV} \). What is the maximum kinetic energy in eV? (Take \( h c = 1240 \, \text{eV nm} \))

Q9. The minimum wavelength of X-rays from a \( 25 \, \text{kV} \) tube is: (Take \( h = 6.63 \times 10^{-34} \, \text{J s} \), \( c = 3 \times 10^8 \, \text{m/s} \), \( e = 1.6 \times 10^{-19} \, \text{C} \))

Q10. The maximum frequency of X-rays produced by a \( 20 \, \text{kV} \) tube is: (Take \( h = 6.63 \times 10^{-34} \, \text{J s} \), \( e = 1.6 \times 10^{-19} \, \text{C} \))