Modern Physics

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Q1. What is the maximum wavelength of light that can cause the photoelectric effect in a metal with a work function of 4.0 eV? (2023)

Solution:

Maximum wavelength (λ) = hc/φ. λ = (1240 eV.nm) / 4.0 eV = 310 nm.

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Q2. What is the principal quantum number of an electron in the third energy level? (2023)

Solution:

The principal quantum number (n) indicates the energy level. For the third energy level, n = 3.

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Q3. What is the main component of a nuclear reactor that slows down neutrons? (2023)

Solution:

The moderator is the main component in a nuclear reactor that slows down neutrons to sustain the nuclear chain reaction.

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Q4. What is the minimum energy required to remove an electron from a metal surface with a work function of 2 eV? (2021)

Solution:

The minimum energy required is equal to the work function, which is 2 eV.

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Q5. If the wavelength of light is halved, what happens to the energy of the photons? (2020)

Solution:

Energy is inversely proportional to wavelength. Halving the wavelength doubles the energy.

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Q6. What is the de Broglie wavelength of an electron moving with a velocity of 1 x 10^6 m/s? (mass of electron = 9.11 x 10^-31 kg) (2022)

Solution:

λ = h / p = h / (mv) = 6.63 x 10^-34 / (9.11 x 10^-31 * 1 x 10^6) = 6.63 x 10^-24 m.

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Q7. What is the minimum energy required to remove an electron from a metal surface with a work function of 2.5 eV? (2022)

Solution:

The minimum energy required to remove an electron is equal to the work function of the metal, which is 2.5 eV.

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Q8. What is the significance of the Rydberg constant? (2022)

Solution:

The Rydberg constant is used to calculate the wavelengths of spectral lines in hydrogen and other hydrogen-like atoms.

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Q9. What is the mass-energy equivalence formula proposed by Einstein? (2019)

Solution:

The mass-energy equivalence formula is E = mc^2, which states that energy (E) is equal to mass (m) times the speed of light (c) squared.

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Q10. What is the principal quantum number of an electron in the ground state of a hydrogen atom? (2022)

Solution:

The ground state of hydrogen corresponds to n = 1.