What type of image is formed by a concave mirror when the object is placed between the pole and the focus?
The image is virtual, erect, and magnified.
Why is the refractive index of air almost equal to 1?
The refractive index of air is almost equal to 1 because the speed of light in air is very close to its speed in a vacuum.
What is total internal reflection?
Total internal reflection is the phenomenon where light, traveling from a denser to a rarer medium, is completely reflected back into the denser medium when the angle of incidence exceeds the critical angle.
Why does light bend during refraction?
Light bends during refraction because it changes speed when it passes from one medium to another. The bending occurs due to the difference in optical densities of the two media.
What is the refractive index?
The refractive index is the ratio of the speed of light in a vacuum to the speed of light in a given medium. It indicates how much light slows down in that medium.
Why do planets not twinkle like stars?
Planets do not twinkle because they are much closer to Earth and appear as extended sources of light, not point sources like stars. The variations in light from different parts of the planet cancel out, so the planet appears steady.
What causes presbyopia, and how is it corrected?
Presbyopia is caused by the gradual weakening of the ciliary muscles and the reduced elasticity of the lens, making it difficult to focus on nearby objects. It is corrected using bifocal or progressive lenses.
What is the near point and far point of the human eye?
The near point is the closest distance at which an object can be seen clearly, typically about 25 cm for a normal adult. The far point is the farthest distance at which objects can be seen clearly, which is at infinity for a normal eye.
Can a person have both myopia and hypermetropia?
Yes, a person can have both myopia and hypermetropia, particularly as they age. This condition is called presbyopia, and it is usually corrected using bifocal or progressive lenses.
What causes the inverted image formed on the retina to appear upright to us?
The brain processes the signals received from the retina and flips the inverted image so that we perceive it as upright and correctly oriented.
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