NEET Dual Nature of Matter — Set 5

Question 1

Light of wavelength $ 400 \, \text{nm} $ is incident on a metal with a stopping potential of $ 1.2 \, \text{V} $. What is the threshold wavelength? (Take $ h c = 1240 \, \text{eV nm} $)

Accepted Answer

$ E = \frac{h c}{\lambda} = \frac{1240}{400} = 3.1 \, \text{eV} $. $ K_{\max} = e V_0 = 1.2 \, \text{eV} $. $ \phi_0 = E - K_{\max} = 3.1 - 1.2 = 1.9 \, \text{eV} $. $ \lambda_0 = \frac{h c}{\phi_0} = \frac{1240}{1.9} \approx 652.63 \, \text{nm} $.

Question 2

What is the nature of the relationship between the stopping potential and the frequency of incident light in the photoelectric effect?

Accepted Answer

The stopping potential $ V_0 $ varies linearly with frequency ($ e V_0 = h v - \phi_0 $), as shown by experimental graphs and Einstein’s equation.

Question 3

Which property of incident light determines the maximum kinetic energy of photoelectrons, assuming the metal remains the same?

Accepted Answer

According to Einstein’s photoelectric equation, $ K_{\max} = h v - \phi_0 $, the maximum kinetic energy depends on the frequency of the incident light.

NEET Physics: Dual Nature of Matter — Practice Set 5

Q1. Light of wavelength \( 400 \, \text{nm} \) is incident on a metal with a stopping potential of \( 1.2 \, \text{V} \). What is the threshold wavelength? (Take \( h c = 1240 \, \text{eV nm} \))

Q2. What is the nature of the relationship between the stopping potential and the frequency of incident light in the photoelectric effect?

Q3. Which property of incident light determines the maximum kinetic energy of photoelectrons, assuming the metal remains the same?

Q4. Light of frequency \( 6.2 \times 10^{14} \, \text{Hz} \) is incident on a metal with work function \( 2.1 \, \text{eV} \). What is the stopping potential? (Take \( h = 6.63 \times 10^{-34} \, \text{J s} \), \( e = 1.6 \times 10^{-19} \, \text{C} \))

Q5. Which of the following particles was historically identified as a universal constituent of matter through cathode ray experiments?

Q6. A photon has a momentum of \( 1.8 \times 10^{-27} \, \text{kg m/s} \). What is its wavelength? (Take \( h = 6.63 \times 10^{-34} \, \text{J s} \))

Q7. What characteristic of light quanta (photons) is directly proportional to their frequency?

Q8. A light source emits photons of energy \( 4.5 \times 10^{-19} \, \text{J} \) at a rate of \( 2.0 \times 10^{16} \) photons per second. What is the wavelength of the light? (Take \( h = 6.63 \times 10^{-34} \, \text{J s} \), \( c = 3 \times 10^8 \, \text{m/s} \))

Q9. A photon of wavelength \( 300 \, \text{nm} \) is incident on a metal. What is its energy in eV? (Take \( h c = 1240 \, \text{eV nm} \))

Q10. The threshold frequency of a metal is \( 3.0 \times 10^{14} \, \text{Hz} \). What is the maximum kinetic energy of electrons emitted by light of wavelength \( 500 \, \text{nm} \)? (Take \( h = 6.63 \times 10^{-34} \, \text{J s} \), \( c = 3 \times 10^8 \, \text{m/s} \))