Exploring Relativity and Quantum Physics

Which of the following best describes time dilation in the context of special relativity?

• Time appears to pass more quickly for objects moving at high speeds compared to stationary observers.

• Time appears to pass more slowly for objects moving at high speeds compared to stationary observers.

• Time is constant regardless of the observer's frame of reference.

• Time is an illusion and does not actually change.

Answer explanation

In special relativity, time dilation means that time appears to pass more slowly for objects moving at high speeds compared to stationary observers. This is a fundamental concept that illustrates how time is relative.

In the photoelectric effect, what is the role of the frequency of the incident light?

• It determines the number of electrons emitted.

• It determines the kinetic energy of the emitted electrons.

• It has no effect on the photoelectric effect.

• It determines the colour of the emitted electrons.

Answer explanation

In the photoelectric effect, the frequency of the incident light determines the kinetic energy of the emitted electrons. Higher frequency light provides more energy, resulting in electrons being emitted with greater kinetic energy.

Which of the following statements about wave-particle duality is correct?

• Particles exhibit wave-like properties only when they are at rest.

• Waves exhibit particle-like properties only when they are in motion.

• Particles and waves exhibit both wave-like and particle-like properties depending on the experiment.

• Wave-particle duality is only applicable to light.

Answer explanation

The correct statement is that particles and waves exhibit both wave-like and particle-like properties depending on the experiment. This reflects the fundamental concept of wave-particle duality, applicable to all quantum entities.

Which particle is not part of the Standard Model?

• Electron

• Photon

• Graviton

• Neutrino

Answer explanation

The graviton is a hypothetical particle that mediates gravity and is not included in the Standard Model of particle physics, which describes electromagnetic, weak, and strong interactions. The electron, photon, and neutrino are all part of the Standard Model.

What is the equation for time dilation in special relativity?

Answer explanation

The correct equation for time dilation in special relativity is \( t' = \frac{t}{\sqrt{1 - \frac{v^2}{c^2}}} \). This shows how time \( t' \) experienced by a moving observer is related to the proper time \( t \) experienced by a stationary observer.

In the photoelectric effect, what happens when the intensity of light is increased while keeping the frequency constant?

• The kinetic energy of the emitted electrons increases.

• The number of emitted electrons increases.

• The frequency of the emitted electrons increases.

• The threshold frequency decreases.

Answer explanation

In the photoelectric effect, increasing light intensity (while keeping frequency constant) results in more photons hitting the surface, leading to a higher number of emitted electrons. The kinetic energy of emitted electrons remains unchanged.

Which experiment demonstrated the wave nature of electrons?

• Rutherford's gold foil experiment

• Young's double-slit experiment

• Davisson-Germer experiment

• Millikan's oil drop experiment

Answer explanation

The Davisson-Germer experiment demonstrated the wave nature of electrons by showing electron diffraction patterns, confirming that electrons exhibit wave-like behavior, similar to light in Young's double-slit experiment.

Which of the following particles is a fermion?

• Photon

• Gluon

• Electron

• Higgs boson

Answer explanation

The electron is a fermion. In contrast, the photon, gluon, and Higgs boson are bosons.

What is the significance of the threshold frequency in the photoelectric effect?

• It is the maximum frequency required to emit electrons.

• It is the minimum frequency required to emit electrons.

• It is the frequency at which light is absorbed without emitting electrons.

• It is the frequency at which the speed of light is achieved.

Answer explanation

The threshold frequency is the minimum frequency required to emit electrons in the photoelectric effect. If the frequency of incident light is below this threshold, no electrons are emitted, regardless of the light's intensity.

Answer explanation

The de Broglie wavelength is given by the formula \( \lambda = \frac{h}{p} \), where \( h \) is Planck's constant and \( p \) is the momentum of the particle. This relationship shows how wavelength is inversely proportional to momentum.