TRB PG Assistant - Planck's hypothesis, black body radiation and photoelectric effect Online Test (MCQ Quiz)

1. What phenomenon did Max Planck's hypothesis primarily aim to explain?

A) The motion of planets B) The emission of light from heated objects C) The behavior of chemical reactions D) The structure of the atom

2. According to Planck's hypothesis, energy is emitted or absorbed in discrete packets called:

A) Waves B) Particles C) Quanta D) Orbits

3. What is the mathematical relationship between the energy (E) of a quantum of light and its frequency (ν) proposed by Planck?

A) E = hν B) E = h/ν C) E = ν/h D) E = mν

4. What does the constant 'h' represent in Planck's equation E = hν?

A) The speed of light B) Planck's constant C) The charge of an electron D) Avogadro's number

5. What is the approximate value of Planck's constant (h)?

A) 6.626 x 10⁻³⁴ J·s B) 3.00 x 10⁸ m/s C) 9.109 x 10⁻³¹ kg D) 1.602 x 10⁻¹⁹ C

6. Black body radiation refers to the electromagnetic radiation emitted by a theoretical object that:

A) Reflects all incident radiation B) Absorbs all incident radiation C) Emits radiation only in the visible spectrum D) Emits radiation only when heated to very high temperatures

7. The classical physics explanation for black body radiation led to a prediction known as the 'ultraviolet catastrophe'. What was this catastrophe?

A) It predicted that intensity would decrease at higher frequencies. B) It predicted that intensity would increase indefinitely with frequency. C) It failed to predict any radiation at higher frequencies. D) It predicted that only visible light would be emitted.

8. How did Planck's quantum hypothesis resolve the ultraviolet catastrophe?

A) By assuming energy is continuous B) By assuming energy is quantized C) By introducing a new force D) By modifying the definition of frequency

9. At low frequencies, Planck's theory of black body radiation:

A) Agreed with classical physics predictions B) Disagreed with classical physics predictions C) Predicted zero intensity D) Predicted infinite intensity

10. The photoelectric effect is the emission of electrons from a material when:

A) It is heated strongly B) It is placed in a magnetic field C) Light shines on it D) It is subjected to high pressure

11. Which scientist is most famously associated with the explanation of the photoelectric effect using quantum theory?

A) Max Planck B) Niels Bohr C) Albert Einstein D) Werner Heisenberg

12. According to Einstein's explanation of the photoelectric effect, light consists of discrete energy packets called:

A) Electrons B) Protons C) Photons D) Neutrons

13. What is the minimum energy required to eject an electron from a metal surface called?

A) Kinetic energy B) Potential energy C) Work function D) Activation energy

14. The energy of a photon is directly proportional to its:

A) Amplitude B) Wavelength C) Frequency D) Polarization

15. If the frequency of incident light is below the threshold frequency for a particular metal, what happens to the photoelectric effect?

A) Electrons are emitted with high kinetic energy. B) Electrons are emitted with low kinetic energy. C) No electrons are emitted. D) All electrons are emitted.

16. What is the threshold frequency?

A) The maximum frequency of light that can cause electron emission. B) The minimum frequency of light required to cause electron emission. C) The frequency of light where the work function is zero. D) The frequency of light where electrons are emitted with maximum kinetic energy.

17. The kinetic energy of the emitted photoelectrons is independent of the:

A) Frequency of incident light B) Intensity of incident light C) Work function of the metal D) Planck's constant

18. The number of photoelectrons emitted per second is directly proportional to the:

A) Frequency of incident light B) Intensity of incident light C) Work function of the metal D) Threshold frequency

19. Einstein's photoelectric equation is given by: KE_max = hν - Φ. What does Φ represent?

A) Kinetic energy B) Frequency C) Work function D) Photon energy

20. What is the relationship between wavelength (λ) and frequency (ν) for electromagnetic radiation?

A) c = λν B) c = λ/ν C) c = ν/λ D) c = λ + ν

21. If the wavelength of incident light is decreased, while keeping the intensity constant, what happens to the kinetic energy of emitted photoelectrons (assuming frequency is above threshold)?

A) It decreases B) It increases C) It remains the same D) It becomes zero

22. The concept of energy quantization was a radical departure from classical physics because classical physics assumed energy to be:

A) Discrete B) Quantized C) Continuous D) Atomic

23. Which of the following is NOT a consequence of Planck's hypothesis?

A) Explanation of black body radiation spectrum B) Foundation for quantum mechanics C) Explanation of the photoelectric effect D) Prediction of wave-particle duality of matter

24. In the context of black body radiation, as temperature increases, the peak of the emitted spectrum shifts towards:

A) Lower frequencies (longer wavelengths) B) Higher frequencies (shorter wavelengths) C) Infrared region only D) Ultraviolet region only

25. The photoelectric effect provides evidence for the particle nature of light, where light behaves as:

A) A continuous wave B) Discrete photons C) A stream of electrons D) A magnetic field

26. A metal surface has a work function of 2.5 eV. If photons of energy 4.0 eV strike the surface, what is the maximum kinetic energy of the emitted electrons?

A) 1.0 eV B) 1.5 eV C) 2.5 eV D) 4.0 eV

27. If the intensity of light shining on a metal surface is increased, but the frequency remains below the threshold frequency, what is the effect on electron emission?

A) More electrons are emitted. B) Electrons are emitted with higher kinetic energy. C) No electrons are emitted. D) Electrons are emitted with lower kinetic energy.

28. The energy of a photon with a frequency of 6.0 x 10¹⁴ Hz is approximately:

A) 3.97 x 10⁻¹⁹ J B) 6.63 x 10⁻³⁴ J C) 1.00 x 10⁻⁵ J D) 1.60 x 10⁻¹⁹ J

29. The phenomenon that demonstrated the quantum nature of electromagnetic radiation was:

A) Diffraction B) Interference C) Photoelectric effect D) Polarization

30. Planck's constant (h) has units of:

A) Joules (J) B) Hertz (Hz) C) Joules-second (J·s) D) Meters per second (m/s)

31. Classical electromagnetism predicts that a heated object should emit radiation of:

A) Infinite intensity at high frequencies B) Zero intensity at high frequencies C) Constant intensity across all frequencies D) Only visible light

32. The work function of a metal is dependent on the:

A) Frequency of incident light B) Intensity of incident light C) Type of metal D) Temperature of the light source

33. What is the energy of a photon of blue light with a wavelength of 450 nm?

A) 4.41 x 10⁻¹⁹ J B) 2.97 x 10⁻¹⁹ J C) 7.36 x 10⁻¹⁹ J D) 1.33 x 10⁻¹⁹ J

34. The photoelectric effect could NOT be explained by the wave theory of light because:

A) Wave intensity is related to amplitude, not energy per photon. B) Waves have no energy. C) Waves always travel at the speed of light. D) Waves cannot be polarized.

35. When a photon strikes a metal surface, its entire energy is transferred to:

A) The metal lattice B) A single electron C) Multiple electrons D) The surrounding air

36. The concept that light can exhibit both wave-like and particle-like properties is known as:

A) Wave-particle duality B) Quantum entanglement C) Superposition D) Uncertainty principle

37. Which of the following statements about black body radiation is INCORRECT?

A) It is the radiation emitted by an idealized object that absorbs all incident electromagnetic radiation. B) The spectrum of black body radiation depends only on its temperature. C) Classical physics successfully explained the observed spectrum. D) Planck's quantum hypothesis was crucial for explaining the spectrum.

38. If the frequency of incident photons is doubled, and is above the work function, the maximum kinetic energy of emitted photoelectrons will:

A) Double B) Halve C) Increase by more than double D) Increase, but not necessarily double

39. The discovery of the photoelectric effect by Hertz in 1887 was initially observed as:

A) An increase in voltage across a spark gap when illuminated by UV light. B) A decrease in current across a spark gap when illuminated by UV light. C) The emission of heat from the metal. D) The generation of sound waves.

40. Planck's quantum hypothesis was initially proposed to solve the problem of:

A) The stability of atoms B) The nature of chemical bonds C) Black body radiation D) The speed of light

41. Which of the following quantities is quantized according to Planck's hypothesis?

A) Mass B) Velocity C) Energy D) Charge

42. The photoelectric effect demonstrates that light energy is delivered in discrete packets, which are:

A) Electrons B) Protons C) Photons D) Neutrinos

43. If a metal has a work function of 3.0 eV, what is the minimum frequency of light required to initiate the photoelectric effect?

A) 7.25 x 10¹⁴ Hz B) 3.63 x 10¹⁴ Hz C) 1.45 x 10¹⁵ Hz D) 2.42 x 10¹⁵ Hz

44. The spectral distribution of black body radiation at a given temperature is:

A) Uniform across all wavelengths B) Concentrated at a single wavelength C) A continuous curve with a peak at a specific wavelength D) Zero at all wavelengths

45. The photoelectric effect is a direct experimental confirmation of:

A) Newton's laws of motion B) The wave nature of light C) The particle nature of light D) The conservation of momentum

46. In the photoelectric effect, the energy of the incident photon is used to overcome the work function and provide:

A) The potential energy of the electron B) The kinetic energy of the electron C) The binding energy of the atom D) The thermal energy of the metal

47. The relationship E = hν implies that higher frequency light carries:

A) Less energy per photon B) More energy per photon C) The same energy per photon D) No energy per photon

48. The 'ultraviolet catastrophe' refers to the failure of classical physics to explain:

A) The photoelectric effect B) The discrete spectral lines of atoms C) The distribution of energy in black body radiation D) The stability of the Bohr model

49. According to Planck's hypothesis, the energy levels of an oscillator are:

A) Continuous B) Discrete and equally spaced C) Discrete and unequally spaced D) Zero

Planck's hypothesis, black body radiation and photoelectric effect - Online Test

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