NEET Dual Nature of Matter — Set 3

Question 1

A light source emits $ 6.0 \times 10^{15} $ photons per second with a power of $ 3.0 \, \text{mW} $. What is the energy of each photon in joules?

Accepted Answer

$ E = \frac{P}{N} = \frac{3.0 \times 10^{-3}}{6.0 \times 10^{15}} = 5.0 \times 10^{-19} \, \text{J} $.

Question 2

Light of frequency $ 7.5 \times 10^{14} \, \text{Hz} $ produces a stopping potential of $ 0.9 \, \text{V} $. What is the work function in eV? (Take $ h = 6.63 \times 10^{-34} \, \text{J s} $)

Accepted Answer

$ E = h v = 6.63 \times 10^{-34} \times 7.5 \times 10^{14} = 4.9725 \times 10^{-19} \, \text{J} $. $ E = \frac{4.9725 \times 10^{-19}}{1.6 \times 10^{-19}} \approx 3.108 \, \text{eV} $. $ K_{\max} = e V_0 = 0.9 \, \text{eV} $. $ \phi_0 = E - K_{\max} = 3.108 - 0.9 \approx 2.208 \, \text{eV} $.

Question 3

The maximum speed of photoelectrons is $ 7.0 \times 10^5 \, \text{m/s} $. What is the maximum kinetic energy in joules? (Take $ m_e = 9.11 \times 10^{-31} \, \text{kg} $)

Accepted Answer

$ K_{\max} = \frac{1}{2} m v_{\max}^2 = \frac{1}{2} \times 9.11 \times 10^{-31} \times (7.0 \times 10^5)^2 $. $ K_{\max} = \frac{1}{2} \times 9.11 \times 10^{-31} \times 4.9 \times 10^{11} \approx 2.231 \times 10^{-19} \, \text{J} $.

NEET Physics: Dual Nature of Matter — Practice Set 3

Q1. A light source emits \( 6.0 \times 10^{15} \) photons per second with a power of \( 3.0 \, \text{mW} \). What is the energy of each photon in joules?

Q2. Light of frequency \( 7.5 \times 10^{14} \, \text{Hz} \) produces a stopping potential of \( 0.9 \, \text{V} \). What is the work function in eV? (Take \( h = 6.63 \times 10^{-34} \, \text{J s} \))

Q3. The maximum speed of photoelectrons is \( 7.0 \times 10^5 \, \text{m/s} \). What is the maximum kinetic energy in joules? (Take \( m_e = 9.11 \times 10^{-31} \, \text{kg} \))

Q4. Why do macroscopic objects not exhibit measurable wave-like properties according to de Broglie’s hypothesis?

Q5. In the photoelectric effect, what happens to the photocurrent when the intensity of incident light increases, keeping frequency constant?

Q6. A photon’s energy is \( 3.0 \, \text{eV} \). What is its momentum? (Take \( c = 3 \times 10^8 \, \text{m/s} \), \( 1 \, \text{eV} = 1.6 \times 10^{-19} \, \text{J} \))

Q7. The maximum speed of photoelectrons is \( 6.0 \times 10^5 \, \text{m/s} \) when light of wavelength \( 400 \, \text{nm} \) is used. What is the work function in eV? (Take \( h c = 1240 \, \text{eV nm} \), \( m_e = 9.11 \times 10^{-31} \, \text{kg} \))

Q8. The maximum kinetic energy of photoelectrons is \( 2.5 \times 10^{-19} \, \text{J} \). What is the stopping potential? (Take \( e = 1.6 \times 10^{-19} \, \text{C} \))

Q9. Which process allows electrons to escape from a metal surface when illuminated by light of suitable frequency?

Q10. Which of the following is the minimum energy required for an electron to escape from a metal surface?