Explanation

A material that absorbs all wavelengths (colors) of visible light reflects none, so no light reaches your eyes.

This absence of reflected light makes the object appear black.

Explanation

Explanation

Diffusion is the movement of particles from high to low concentration and occurs rapidly in gases, slowly in liquids, but is negligible in solids.

In solids, particles are tightly packed and cannot move freely, so diffusion does not occur significantly.

Explanation

Many handheld metal detectors commonly use 9V batteries, and their operating voltage often falls within the 6V-9V range.

Some sources might mention a lower range like 3-5V for simpler detectors, while others specify a slightly higher range like 7-9V. 

Explanation

• A Periscope is an optical instrument used to observe objects that are not in direct line of sight.
• Such as monitoring the surface of the water from a submarine.

Explanation

A Vernier caliper provides precise linear measurements of small objects.

It can measure internal, external, and depth dimensions with high accuracy (usually up to 0.1 mm or 0.01 cm).

Explanation

Caves are mainly formed when water erodes soluble rocks like limestone over long periods.

This process is called chemical weathering.

It is leads to underground hollow spaces.

Explanation

A black dwarf is the final stage of a low-mass star, after it has cooled and no longer emits significant heat or light.

It forms when a white dwarf loses all its residual thermal energy over billions of years.

Explanation

According to Newton's second law, 

F=ma, a constant non-zero force results in uniform acceleration of the mass.

Explanation

• When light travels from a denser to a rarer medium, it bends away from the normal due to refraction.
• The production of an image by or as if by a mirror is called reflection.