Science (English Medium) कक्षा १२ - CBSE Question Bank Solutions

Answer the following question.
Why is the wave theory of electromagnetic radiation not able to explain the photoelectric effect? How does a photon picture resolve this problem?

In Young's double-slit experiment, the two slits are separated by a distance of 1.5 mm, and the screen is placed 1 m away from the plane of the slits. A beam of light consisting of two wavelengths of 650 nm and 520 nm is used to obtain interference fringes.
Find the distance of the third bright fringe for λ = 520 nm on the screen from the central maximum.

Write the conditions on path difference under which constructive interference occurs in Young’s double-slit experiment.

In the case of a photo electric effect experiment, explain the following facts, giving reasons.
The wave theory of light could not explain the existence of the threshold frequency.

Two-point charges q₁ and q₂ are kept at a distance of r₁₂ in air. Deduce the expression for the electrostatic potential energy of this system.

If an external electric field (E) is applied on the system, write the expression for the total energy of this system.

Choose the correct alternative:

Alloys usually have much (lower/higher) temperature coefficients of resistance than pure metals.

Choose the correct alternative:

The resistivity of the alloy manganin is nearly independent of/increases rapidly with increase of temperature.

Choose the correct alternative:

The resistivity of a typical insulator (e.g., amber) is greater than that of a metal by a factor of the order of (10²²/10²³).

Which of the following methods can be used to charge a metal sphere positively without touching it? Select the most appropriate.

According to Gauss’s law for magnetism ______.

Total internal reflection can take place only if light is travelling from ______.

Optical fibre communication uses the principle of ______.

Wavefront is ______.

When a beam of light is used to determine the position of an object, the maximum accuracy is achieved, if the light is ______.

In Photoelectric effect ______.

In the experimental set up for studying photoelectric effect, if keeping the frequency of the incident radiation and the accelerating potential fixed, the intensity of light is varied, then ______.

For a given frequency of light and a positive plate potential in the set up below, If the intensity of light is increased then ______.

In various experiments on photo electricity, the stopping potential for a given frequency of the incident radiation is ______.

The surface charge density of a thin charged disc of radius R is σ. The value of the electric field at the center of the disc is `sigma/(2∈_0)`. With respect to the field at the center, the electric field along the axis at a distance R from the center of the disc ______.