Physics - Study Mode

[#71] Energy is continuously created in the sun due to:
Correct Answer

(A) Nuclear fusion

Explanation

Solution: The central mass of the sun becomes increasingly hot and dense, eventually initiating thermonuclear fusion in its core. It is thought that almost all other stars form by this process. nuclear fusion is a nuclear reaction in which two or more atomic nuclei join together, or “fuse”, to form a single heavier nucleus. During this process, matter is not conserved because some of the mass of the fusing nuclei is converted to energy which is released. Fusion is the process that powers active stars. The fusion of two nuclei with lower masses than iron (which, along with nickel, has the largest binding energy per nucleon) generally releases energy, while the fusion of nuclei heavier than iron absorbs energy.

[#72] The mass defect is the result of what action occurring?
Correct Answer

(A) Mass being converted to energy when protons and neutrons bind together in a nucleus

Explanation

Solution: The concept of mass defect comes from the concept of nuclear binding energy, which is the energy required to disassemble the nucleus of an atom into its components. The components are protons and neutrons. Energy is applied to break the nucleus.

[#73] Which one of the following wavelengths of light is most effective in photosynthesis ?
Correct Answer

(A) Blue

Explanation

Solution: The best wavelengths of visible light for photosynthesis fall within the blue range (425–450 nm) and red range (600–700 nm). Therefore, the best light sources for photosynthesis should ideally emit light in the blue and red ranges.

[#74] The optical phenomenon that is primarily responsible for the observation of rainbow on a rainy day is
Correct Answer

(C) Dispersion

Explanation

Solution: The optical phenomenon that is primarily responsible for the observation of rainbow on a rainy day is dispersion. Rainbow is caused mainly by reflection, refraction and dispersion.

[#75] An electron microscope gives higher magnification than an optical microscope, because :
Correct Answer

(D) The wavelength of electrons is smaller as compared to the wavelength of visible light

Explanation

Solution: An electron microscope gives higher magnification than an optical microscope because the wavelength of electrons is smaller than wavelength of visible light. Hence, making electron microscope to resolve objects that are very small more clearly.