Which of these waves cause skin cancer and sun tans? ultraviolet rays infrared waves gamma radiation microwaves

## Step 1
The problem asks us to identify which type of wave causes skin cancer and sun tans. The options provided are ultraviolet rays, infrared waves, gamma radiation, and microwaves.

## Step 2
Ultraviolet (UV) rays are known to cause skin cancer and sun tans. This is because UV rays have enough energy to damage the DNA in skin cells, which can lead to skin cancer. Additionally, UV rays can cause the skin to produce more melanin, which results in a sun tan.

## Step 3
Infrared waves, gamma radiation, and microwaves do not have the same effect on the skin as UV rays. Infrared waves are a type of electromagnetic radiation that is not visible to the human eye and does not cause skin cancer or sun tans. Gamma radiation is a type of high-energy electromagnetic radiation that is not typically encountered in everyday life and does not cause skin cancer or sun tans. Microwaves are a type of electromagnetic radiation used in microwave ovens and do not cause skin cancer or sun tans.