Question

Which of the given-below options is/are always required for observing a shadow.

• A. Sun
• B. Screen
• C. Source of light
• D. Opaque object

Answer 1

The correct option is D

Opaque object

Explanation of the correct option

In the case of option B,

1. The screen is the basic requirement for observing a shadow since the shadow will appear on the screen.
2. But it is not always required because any object can work as a screen, the primary requirement is the source of light.

In the case of option C,

1. A shadow is a dark area that is caused when an opaque object blocks the light from a light source. The following requirements must be satisfied to form the shadow.
2. An opaque substance, a screen, and a light source are required. The item needs to be positioned in the light's path. The screen then develops a shadow.
3. There are many sources of light that can be used to observe a shadow such as a torch, sun, moon, bulb, etc. But without the source of light, the shadow can never be formed. It is a primary requirement for the observation of shadows.

In the case of option D,

1. Opaque objects prevent light from passing through them. As a result, they cast a shadow on the opposite side of the light source.
2. Some examples of opaque objects are wood, stone, etc

Step 2: Explanation for the incorrect options

In the case of option A,

1. A source of light is always required for forming a shadow.
2. A light source is defined as anything that produces light, whether natural such as the sun and stars or artificial such as a lamp post, torch, etc.
3. So, the sun is not always required because other light sources are available that can fulfill the requirement.

Hence, option B,C & D is the correct answer