Physics Mock Tests

The SI unit of temperature is:

Which of the following gases is the most abundant gas in Earth's atmosphere?

The SI unit of electric current is:

Sound travels fastest in which of the following media?

Newton's first law of motion is also known as the law of:

The SI unit of power is:

With reference to the principles of thermodynamics, consider the following statements: 1. The first law of thermodynamics is essentially the law of conservation of energy applied to thermal systems. 2. The second law of thermodynamics states that heat cannot spontaneously flow from a colder body to a hotter body. 3. The third law of thermodynamics states that the entropy of a system is zero at absolute zero temperature. Which of the statements given above is/are correct?

The following passage is an excerpt from a physics textbook discussing the wave-particle duality of light and its significance in the development of modern physics. The nature of light has been one of the most deeply debated questions in the history of physics, and the resolution of this debate in the form of wave-particle duality represents one of the foundational concepts of quantum mechanics. For centuries, scientists disagreed about whether light consists of waves or particles. In the seventeenth century, Isaac Newton proposed a corpuscular theory of light, arguing that light is composed of tiny particles called corpuscles that travel in straight lines. This theory successfully explained the laws of reflection and refraction. However, in the early nineteenth century, Thomas Young's famous double-slit experiment demonstrated that light produces interference patterns — alternating bright and dark bands — when passed through two narrow slits, a phenomenon that can only be explained by wave behavior. Interference occurs when two waves overlap, with crests reinforcing crests (constructive interference) to produce bright regions and crests meeting troughs (destructive interference) to produce dark regions. The wave theory of light was further strengthened by James Clerk Maxwell's equations in the 1860s, which showed that light is an electromagnetic wave consisting of oscillating electric and magnetic fields perpendicular to each other and to the direction of propagation. However, in 1905, Albert Einstein published a paper explaining the photoelectric effect — the emission of electrons from a metal surface when light shines upon it — by proposing that light consists of discrete packets of energy called photons. The wave theory could not explain why the energy of emitted electrons depended on the frequency (color) of the light rather than its intensity (brightness), but Einstein's particle theory accounted for this perfectly: each photon carries a specific amount of energy proportional to its frequency. The double-slit experiment was later repeated with individual photons, one at a time, and the remarkable result was that even single photons produced an interference pattern over time, suggesting that each photon somehow passes through both slits simultaneously and interferes with itself. This paradox — that light exhibits both wave-like and particle-like properties depending on how it is observed — is the essence of wave-particle duality. Niels Bohr's principle of complementarity states that waves and particles are complementary descriptions of the same phenomenon, and both are necessary for a complete understanding of light's behavior. Wave-particle duality was later extended to matter by Louis de Broglie, who proposed that all particles, including electrons, have an associated wavelength. Which of the following can be inferred from the passage about the photoelectric effect?