NEET Dual Nature of Matter — Set 7

Question 1

The threshold wavelength of a metal is $ 620 \, \text{nm} $. What is the work function in eV? (Take $ h c = 1240 \, \text{eV nm} $)

Accepted Answer

$ \phi_0 = \frac{h c}{\lambda_0} = \frac{1240}{620} = 2.0 \, \text{eV} $.

Question 2

A photon of frequency $ 8.0 \times 10^{14} \, \text{Hz} $ has what energy in joules? (Take $ h = 6.63 \times 10^{-34} \, \text{J s} $)

Accepted Answer

$ E = h v = 6.63 \times 10^{-34} \times 8.0 \times 10^{14} = 5.304 \times 10^{-19} \, \text{J} $.

Question 3

A photon has a wavelength of $ 250 \, \text{nm} $. What is its energy in joules? (Take $ h = 6.63 \times 10^{-34} \, \text{J s} $, $ c = 3 \times 10^8 \, \text{m/s} $)

Accepted Answer

$ E = \frac{h c}{\lambda} = \frac{6.63 \times 10^{-34} \times 3 \times 10^8}{250 \times 10^{-9}} = 7.974 \times 10^{-19} \, \text{J} $.

NEET Physics: Dual Nature of Matter — Practice Set 7

Q1. The threshold wavelength of a metal is \( 620 \, \text{nm} \). What is the work function in eV? (Take \( h c = 1240 \, \text{eV nm} \))

Q2. A photon of frequency \( 8.0 \times 10^{14} \, \text{Hz} \) has what energy in joules? (Take \( h = 6.63 \times 10^{-34} \, \text{J s} \))

Q3. A photon has a wavelength of \( 250 \, \text{nm} \). What is its energy in joules? (Take \( h = 6.63 \times 10^{-34} \, \text{J s} \), \( c = 3 \times 10^8 \, \text{m/s} \))

Q4. The work function of a metal is \( 1.5 \, \text{eV} \). Light of wavelength \( 400 \, \text{nm} \) is incident on it. What is the maximum kinetic energy of emitted electrons in eV? (Take \( h c = 1240 \, \text{eV nm} \))

Q5. A photon has a momentum of \( 2.0 \times 10^{-27} \, \text{kg m/s} \). What is its energy in joules? (Take \( c = 3 \times 10^8 \, \text{m/s} \))

Q6. A particle of mass \( 1.5 \times 10^{-30} \, \text{kg} \) has the same momentum as a photon of wavelength \( 500 \, \text{nm} \). What is its speed? (Take \( h = 6.63 \times 10^{-34} \, \text{J s} \))

Q7. An electron moves with a speed of \( 3.0 \times 10^6 \, \text{m/s} \). What is its de Broglie wavelength? (Take \( h = 6.63 \times 10^{-34} \, \text{J s} \), \( m_e = 9.11 \times 10^{-31} \, \text{kg} \))

Q8. A photon has a wavelength of \( 200 \, \text{nm} \). What is its momentum? (Take \( h = 6.63 \times 10^{-34} \, \text{J s} \))

Q9. Light of wavelength \( 400 \, \text{nm} \) produces photoelectrons with a stopping potential of \( 0.8 \, \text{V} \) from a metal. What is the work function of the metal in eV? (Take \( h c = 1240 \, \text{eV nm} \))

Q10. The maximum speed of photoelectrons emitted from a surface is \( 5.0 \times 10^5 \, \text{m/s} \). What is the stopping potential? (Take \( m_e = 9.11 \times 10^{-31} \, \text{kg} \), \( e = 1.6 \times 10^{-19} \, \text{C} \))