Do you know?
Light and Optics | Kerala PSC LDC
- Fact 1 of 8💡
Speed of light in vacuum
Light travels at exactly 299,792,458 metres per second in vacuum, usually rounded to 3 × 10⁸ m/s. Its speed drops when it passes through media like water or glass, which is why refraction happens.
- Fact 2 of 8🧵
How optical fibres carry light
Optical fibres guide light along their length using total internal reflection, which occurs when light travels from a denser to a rarer medium at an angle greater than the critical angle.
- Fact 3 of 8👓
Correcting short-sightedness
Myopia (short-sightedness) is corrected with a concave lens, which diverges light so it focuses on the retina. Hypermetropia (long-sightedness) is corrected with a convex lens.
- Fact 4 of 8🔍
Power of a lens is measured in dioptres
The power of a lens is P = 1/f, where f is the focal length in metres, and its unit is the dioptre (D). A convex lens has positive power and a concave lens has negative power.
- Fact 5 of 8🌈
Red bends least in a prism
When white light passes through a glass prism, it splits into VIBGYOR. Red light deviates the least and violet light deviates the most, because the refractive index of glass is highest for violet.
- Fact 6 of 8🌤️
Why the sky looks blue
Shorter wavelengths scatter more strongly in the atmosphere, a process called Rayleigh scattering. Blue light, having the shortest visible wavelengths, is scattered most, so the daytime sky appears blue.
- Fact 7 of 8👁️
The eye's blind spot
The blind spot is the point on the retina where the optic nerve leaves the eye. It has no light-sensitive rods or cones, so no image is formed there.
- Fact 8 of 8🪞
Image formed by a plane mirror
A plane mirror always forms a virtual, erect image that is the same size as the object and is laterally inverted. The image appears as far behind the mirror as the object is in front of it.
