Question

Normally, the temperature decreases with the increase in height from the Earth's surface, because

1. the atmosphere can be heated upwards only from the Earth's surface

2. there is more moisture in the upper atmosphere

3. the air is less dense in the upper atmosphere

Select the correct answer using the codes given below:

1. 1 only
2. 2 and 3 only
3. 1 and 3 only
4. 1, 2 and 3

Answer 1

Correct Answer - Option 3 : 1 and 3 only

The correct answer is 1 and 3 only

The temperature decreases with the increase in height from the Earth's surface:

• Under usual conditions, 1-degree Celcius temperature falls at height of every 165 mt in the troposphere. This is called the normal lapse rate.
• As we increase elevation, there is less air above us thus the pressure decreases.
• As the pressure decreases, air molecules spread out further (i.e. air expands), and the temperature decreases and the atmosphere can be heated upwards only from the Earth's surface. Hence statement 1 is correct.
• Temperature falls off with height at a predictable rate because the air near the surface is heated and becomes light, and the air higher up cools to space and becomes heavy.
  • Hence the air density in the atmosphere decreases with height and it helps in decreasing temperature. Hence statement 3 is correct.
• The water vapour, which accounts for around 1% of air varies greatly in the troposphere and decreases rapidly with altitude. Hence statement 2 is incorrect.