Question

External source of radiation is
A. Radon $ - 222$
B. Cosmic rays
C. Solar radiations
D. All of the above

Answer 1

Hint: In order to solve this question, we need to know about radiates first, Radiations are a form of energy which are originate from a source and travels in space with the speed of light, these radiations are in the form of wave consisting of electric and magnetic field component or in form of particle’s like photons. We will examine each of the given options one by one to know which radiations originate from an external source.

Complete step by step answer:
External sources of radiation are those which originated from outside our body and interact with us whereas radiations which originated from inside within us are called internal sources of radiation.

Radon $ - 222$ During the radioactive decay of radioactive material $radium - 226$ ,it produces radiations which are odourless and colourless called Radon $ - 222$ hence, these are examples of external sources of radiation.

Cosmic rays are highly energetic protons and atomic nuclei rays which originate from the sun and travel at the speed of light in space, hence these rays also originate from external sources of radiation.

Solar radiation or simply means the electromagnetic radiation or sunlight which comes through the sun, hence these radiations also originate from external sources of radiation.So, all given options are an example of an external source of radiation.

Hence, the correct option is D.

Note: It should be remembered that, internal sources of radiations such as potassium $ - 40$ and carbon $ - 14$ these isotopes are present in all human bodies from birth and they emit very less amount of radiations but not in quantity that is noticeable hence, these are some examples of internal source of radiations.