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The straight-line propagation of light is a fundamental optical principle. Option A is wrong. Light (photons) has zero rest mass. Being heavy would actually relate to gravitational effects not straight-line propagation. The statement that light is heavy is physically incorrect. Option B is CORRECT. The image states: प्रकाश सीधी रेखा में चलता है, क्योंकि — प्रकाश का तरंगदैर्ध्य बहुत छोटा होता है. Light appears to travel in straight lines because its wavelength (390-780 nm) is extremely small compared to everyday objects. When wavelength is very small diffraction effects (bending around obstacles) become negligible and light effectively travels in straight rays. This rectilinear propagation is the basis for ray optics (geometric optics). It explains phenomena like shadows sharp edges umbra and penumbra formation and the operation of pinhole cameras. Option C is wrong. Having no mass does not by itself cause straight-line propagation. Gravitational waves also have no mass associated with their carriers but follow curved paths near massive objects. Masslessness is a property of photons but not the reason for straight-line propagation. Option D is wrong. Light travels in straight lines in all transparent media not just vacuum. In fact light travels through glass water air and other media in straight lines (except at boundaries where it bends due to refraction).
FAQ
Common questions and clear answers for this topic.
Optics is the branch of physics that studies the behavior of light, including its reflection, refraction, and interaction with lenses and mirrors.
Reflection is the bouncing back of light when it strikes a surface, while refraction is the bending of light as it passes from one medium to another with a different optical density.
A lens is a transparent optical device with curved surfaces that refracts light to converge or diverge rays, commonly classified as convex (converging) or concave (diverging).
The speed of light in a vacuum is approximately 3 x 10^8 meters per second, denoted by the symbol c.
Total internal reflection occurs when light traveling from a denser medium to a rarer medium strikes the boundary at an angle greater than the critical angle, causing it to be completely reflected back into the denser medium.
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