Why are dewdrops not formed on a cloudy night?

The correct option is Clouds reflect back the Earth’s radiation.

Step-by-Step Explanation:

1. Understanding Dew Formation:
Dewdrops are formed when moisture present in the air condenses onto cool surfaces such as grass, leaves, or metal objects near the ground. During a clear night, the Earth's surface continuously loses heat by radiating longwave infrared energy into outer space. As a result, the surface temperature drops significantly, cooling the surrounding air down to or below its dew point, causing water vapor to condense into dewdrops.

2. Effect of Cloud Cover:
On a cloudy night, the clouds act like a thermal blanket surrounding the Earth. Instead of allowing terrestrial radiation to escape into space, clouds absorb and reflect back the thermal radiation released from the Earth's surface back towards the ground.

3. Impact on Temperature:
Because the radiation is reflected back to the Earth's surface, the ground temperature remains relatively high and does not cool down sufficiently. Since the temperature does not reach the dew point, condensation of water vapor cannot take place, preventing the formation of dewdrops.

Therefore, dewdrops are not formed on cloudy nights because clouds reflect back the Earth's radiation.