Sources and Properties of Light

1.Explain Why Light Can Travel in Vacuum but Not Sound.

• Light and sound energy are sources of energy that propagate as waves.
• Light energy does not require a medium to propagate, but sound energy needs a medium to propagate.
• So, light can travel in a vacuum, but sound cannot.

2.Is Water More Opaque Than Air?

• Yes, water is opaquer than air because it is optically denser than air.
• It means that the speed of light is higher in the air than in the water.

3.What Is Refraction?

• The bending of light rays when they travel from one medium to another is called refraction.
• It happens because the speed of light is different in different media.

4.What Is a Lens, and How Many Types of Lens Are There?

A lens is an optical device made of transparent materials like glass that refracts light rays.
It can focus light to form an image.

Lenses can be categorised into two types—

• Concave lens: A concave lens is curved from both sides, thinner at the centre and thicker at the edges.
• Convex lens: A biconvex lens is curved from both sides but thicker at the centre and thinner at the edges.

5.Why Does a Rose Look Red in the Light of All the Colours?

• A rose is an opaque object.
• It absorbs all light colours exc

6.What Is a Rainbow?

• A rainbow is a multicolour arc that forms due to light dispersion through water vapours.
• A rainbow usually appears in the sky after rainfall.
• The colours in a rainbow are visible in the following sequence—violet-indigo-blue-green-yellow-orange-red, in short, VIBGYOR.