Question

Identify the harmful radiations emitted by sun
(a) Ultraviolet
(b) Infrared
(c) Visible
(d) Radio waves

Answer 1

Hint: The harmful radiation emitted by the sun is more energetic than visible radiation therefore having shorter wavelength is known to be the cause of many skin related disorders.

Complete answer:
Solar radiation emits visible light, ultraviolet light, infrared, radio waves, X-rays, and gamma rays. Out of all these radiations, Ultraviolet (UV) rays are most harmful due to their higher energy. Low energy waves cause a mild shaking of the molecules of a substance but due to high energy of UV rays electrons can be knocked away from the atoms causing molecules to split up. This small change is detrimental to living organisms since it can damage the genetic material (the DNA) in your skin cells. If enough DNA damage builds up over time, it can cause cells to start growing out of control, which can lead to skin cancer, eye cataract and other skin problems.

Fig: The electromagnetic spectrum

Additional information:
Based on the amount of energy UV rays are further categorized into 3 types:
UVA rays: They have the least energy among UV rays. These rays are responsible for skin cells to age and can cause some indirect damage to cells’ DNA.
UVB rays: They have slightly more energy than UVA rays. They can damage the DNA in skin cells directly and are the main rays behind sunburns. They are also considered as the cause of most skin cancers.
UVC rays: They have the highest energy among the UV rays. Due to this reason they react with ozone high in our atmosphere and don’t reach the ground, so they are not normally a risk factor for skin cancer.

So, the correct answer is ‘Ultraviolet’

Note:
1. Energy and wavelength have an inverse relation.
2. Even the higher energy UV rays don’t have enough energy to penetrate deeply into the body, so their main effect is on the skin.