Sources and Properties of Light

1) How are Shadows Formed?

• A shadow is a dark figure formed when an opaque object blocks the path of light.
• The source of the light, an opaque object and a screen are three basic requirements for the formation of a shadow.
• A shadow is always black in colour. Its size depends on the distance between the object and the light source.

2) Explain How Shadows Change Throughout the Day?

• Shadows are longer in the morning and evening, and shorter during the day.
• The size of a shadow depends on the sun's position in the sky.
• The sun is near the horizon during sunrise and sunset, which makes the shadows longer.
• In the afternoon, the sun is over our heads; hence the shadows are smaller.

3) Why Does the Sky Appear Blue?

• When sunlight passes through the atmosphere, tiny air particles of the atmosphere scatter the light waves.
• These particles scatter blue light more than other colours, making the sky appear blue.

4) What Is a Rainbow, and How Is It Formed?

• A multi-coloured arc that appears in the sky due to the dispersion of light through water droplets is called a rainbow.
• Dispersion of light is the splitting of white light into seven constituent colours.
• Rainbow is formed after the rain due to the dispersion of sunlight by the water particles.
• The order of seven colours in the rainbow are violet, indigo, blue, green, yellow, orange, and red.

5) How Does a Magnifying Glass Burn Things?

• A magnifying glass is made using a convex lens.
• A convex lens is thicker in the middle and thinner at the edges and has the ability to converge the light rays passing through it at one point.
• Due to the high concentration of light rays at a point, sufficient heat is produced, which can burn things.