Name the electromagnetic waves used for following and arrange them in increasing order of their penetrating power:
(a)water purification (b) remote sensing
(c) treatment of cancer.

Explanation

To solve the problem, we need to identify the electromagnetic waves associated with each application and then arrange them in order of increasing penetrating power.

### Step-by-Step Solution:

1. **Identify the electromagnetic waves for each application:**
- **(a) Water purification:** The electromagnetic waves used for water purification are **Ultraviolet (UV) rays**. UV rays are effective in killing bacteria and viruses in water.
- **(b) Remote sensing:** The electromagnetic waves used in remote sensing are **Microwaves**. Microwaves are suitable for transmitting data and capturing images of the Earth's surface.
- **(c) Treatment of cancer:** The electromagnetic waves used for the treatment of cancer are **Gamma rays**. Gamma rays have high energy and are used in radiation therapy to target and kill cancer cells.
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