Physics - Study Mode

[#951] The mercury and sodium street lamps light up because of :
Correct Answer

(A) Atomic emission

Explanation

Solution: The light in sodium vapour lamp and mercury vapour lamp is, because of electron emission. In case of Sodium Lamps, filaments of the lamp sputter fast moving electrons, which hit the sodium atoms (vapour) causing the valence electrons of the sodium atoms to excite to higher energy levels and the electrons thus excited relax by emitting the characteristic monochromatic bright yellow light. The mechanism in mercury vapour lamp is more involved and sequential. The sputtered electrons from the filaments, after having been accelerated by high voltage, hit the mercury atoms. Here also, the excited electrons of mercury atoms relax by emitting characteristic but ultraviolet light.

[#952] Nuclear Reactors are based on which of the following phenomenon?
Correct Answer

(C) Controlled Nuclear Fission

Explanation

Solution: Nuclear Reactors uses Controlled Nuclear Fission to generate electricity. A nuclear reactor splits the atoms of nuclear fuel (eg. uranium) to generate energy to turn water into steam to drive turbine generators.

[#953] Which type of radiation has the lowest penetrating ability?
Correct Answer

(A) Alpha

Explanation

Solution: There are three types of nuclear radiation: alpha, beta and gamma. Alpha is the least penetrating, while gamma is the most penetrating.

[#954] Which one of the following instruments is used to study dispersion of light ?
Correct Answer

(C) Spectrometer

Explanation

Solution: Dispersion occurs when different frequencies of light have different phase velocities, due either to material properties (material dispersion) or to the geometry of an optical waveguide (waveguide dispersion). A spectrometer (spectro-photometer, spectrograph or spectroscope) is an instrument used to measure properties of light over a specific portion of the electromagnetic spectrum, typically used in spectroscopic analysis to identify materials. The variable measured is most often the light’s intensity but could also, for instance, be the polarization state.

[#955] Which one of the following is responsible for the working of Newton's colour disc experiment ?
Correct Answer

(C) Persistence of vision

Explanation

Solution: A Newton Disc can be created by painting a disc with the seven different colours. A combination of red, green and blue in the circular disc will yield the same result. This is due to the phenomenon called persistence of vision.