NEET · Physics · Ray Optics & Optical Instruments doubts
6 doubts found
Why does a straw in a glass of water look bent or broken at the surface?
Light from the underwater part of the straw bends as it leaves the water (denser) into air (rarer), refracting away from the normal.
Why do stars twinkle at night but planets shine steadily?
A star is so far away it's effectively a point source; its thin beam gets randomly bent by moving pockets of air of different densities, so its brightness and position flicker — twinkling.
How does an optical fibre carry light around bends without leaking it out?
The light hits the fibre's inner wall at an angle greater than the critical angle, so it undergoes total internal reflection instead of escaping.
A swimming pool always looks shallower than it really is — why, and by how much?
Light from the bottom bends away from the normal as it leaves the water, so your eye sees the bottom raised.
Which spectacle lens fixes short-sightedness, and which fixes long-sightedness?
A short-sighted (myopic) eye focuses images in front of the retina, so it needs a concave (diverging) lens to spread the rays out before they enter the eye.
Why can a magnifying glass make text look bigger, and where must I hold it?
A magnifying glass is a convex lens.