NEET Dual Nature of Matter — Set 9

Question 1

Light of wavelength $ 500 \, \text{nm} $ is incident on a metal with stopping potential $ 0.6 \, \text{V} $. What is the threshold wavelength? (Take $ h c = 1240 \, \text{eV nm} $)

Accepted Answer

$ E = \frac{h c}{\lambda} = \frac{1240}{500} = 2.48 \, \text{eV} $. $ K_{\max} = e V_0 = 0.6 \, \text{eV} $. $ \phi_0 = E - K_{\max} = 2.48 - 0.6 = 1.88 \, \text{eV} $. $ \lambda_0 = \frac{h c}{\phi_0} = \frac{1240}{1.88} \approx 659.57 \, \text{nm} $.

Question 2

The stopping potential for photoelectrons from a metal is $ 2.0 \, \text{V} $ when illuminated with light of frequency $ 6.0 \times 10^{14} \, \text{Hz} $. What is the work function in eV? (Take $ h = 6.63 \times 10^{-34} \, \text{J s} $, $ e = 1.6 \times 10^{-19} \, \text{C} $)

Accepted Answer

$ E = h v = 6.63 \times 10^{-34} \times 6.0 \times 10^{14} = 3.978 \times 10^{-19} \, \text{J} $. $ E = \frac{3.978 \times 10^{-19}}{1.6 \times 10^{-19}} \approx 2.486 \, \text{eV} $. $ K_{\max} = e V_0 = 2.0 \, \text{eV} $. $ \phi_0 = E - K_{\max} = 2.486 - 2.0 = 0.486 \, \text{eV} $.

Question 3

Which of the following is a key feature of photons that distinguishes them from charged particles?

Accepted Answer

Photons are electrically neutral and thus not deflected by electric or magnetic fields, unlike charged particles such as electrons.

NEET Physics: Dual Nature of Matter — Practice Set 9

Q1. Light of wavelength \( 500 \, \text{nm} \) is incident on a metal with stopping potential \( 0.6 \, \text{V} \). What is the threshold wavelength? (Take \( h c = 1240 \, \text{eV nm} \))

Q2. The stopping potential for photoelectrons from a metal is \( 2.0 \, \text{V} \) when illuminated with light of frequency \( 6.0 \times 10^{14} \, \text{Hz} \). What is the work function in eV? (Take \( h = 6.63 \times 10^{-34} \, \text{J s} \), \( e = 1.6 \times 10^{-19} \, \text{C} \))

Q3. Which of the following is a key feature of photons that distinguishes them from charged particles?

Q4. The de Broglie wavelength of a particle of mass \( 2.0 \times 10^{-30} \, \text{kg} \) moving at \( 1.5 \times 10^6 \, \text{m/s} \) is:

Q5. Light of wavelength \( 450 \, \text{nm} \) is incident on a metal. The stopping potential is \( 0.5 \, \text{V} \). What is the threshold wavelength of the metal? (Take \( h c = 1240 \, \text{eV nm} \))

Q6. A light beam emits \( 2.5 \times 10^{15} \) photons per second, each of energy \( 4.0 \times 10^{-19} \, \text{J} \). What is the power of the beam?

Q7. Which of the following properties of photoelectrons is independent of the intensity of incident light?

Q8. What is the significance of the stopping potential in the photoelectric effect?

Q9. Light of frequency \( 8.5 \times 10^{14} \, \text{Hz} \) is incident on a metal with threshold frequency \( 4.0 \times 10^{14} \, \text{Hz} \). What is the stopping potential? (Take \( h = 6.63 \times 10^{-34} \, \text{J s} \), \( e = 1.6 \times 10^{-19} \, \text{C} \))

Q10. Light of frequency \( 5.5 \times 10^{14} \, \text{Hz} \) produces photoelectrons with a maximum speed of \( 4.0 \times 10^5 \, \text{m/s} \). What is the work function in eV? (Take \( h = 6.63 \times 10^{-34} \, \text{J s} \), \( m_e = 9.11 \times 10^{-31} \, \text{kg} \))