Light can be assumed to travel approximately in a straight line because
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → the wavelength of light is much smaller than the dimensions of ordinary objects
Option (1) the wavelength of light is much smaller than the dimensions of ordinary objects — Correct. The wavelength of visible light is extremely small (about \( 0.6\,\mu\mathrm{m} \) for yellow light), far smaller than mirrors, lenses and other everyday objects. Its bending around them (diffraction) is then negligible, so light can be treated as travelling in straight lines (rays).
Option (2) light has a particle nature — Incorrect. Light is an electromagnetic wave. Its nearly straight-line travel is explained in the wave picture itself, by the very small wavelength. No particle model is needed.
Option (3) the wavelength of light is larger than the dimensions of ordinary objects — Incorrect. The wavelength of visible light is less than a micrometre, much smaller than ordinary objects. A wave would bend strongly around obstacles smaller than its wavelength.
Option (4) light has a wave nature — Incorrect. The wave nature by itself leads to bending and spreading of light (diffraction); straight-line travel holds only because the wavelength is so small.
NCERT (2026-27):
Introduction – “… The wavelength of visible light was measured and found to be extremely small; for example, the wavelength of yellow light is about 0.6 μm. Because of the smallness of the wavelength of visible light (in comparison to the dimensions of typical mirrors and lenses), light can be assumed to approximately travel in straight lines.”