General Science Class 7

In which mode heat transfer in liquids and gases?

1. Convection
2. Radiation
3. Conduction
4. None

During the daytime, the air above the land gets heated up its density:

1. Increase
2. Decrease
3. Remain same
4. Fluctuate

During the night time, the air above the land loses heated up its density:

1. Decrease
2. Fluctuate
3. Remain same
4. Increase

The heat from Sun reaches to earth in form of waves called:

1. Conduction
2. Radiation
3. Convection
4. None

Refrigerator works on the phenomenon of ____of heat transfer.

1. Conduction
2. Convection
3. Radiation
4. All of these

The cooling fins at the back of refrigerator are made of black and rough surface because:

1. They are good conductors of heat
2. They are good radiators of heat
3. They are good insulators of heat
4. They are not important for heat transfer

A thermos flask keeps things close to their original temperature by reducing:

1. Conduction
2. Convection
3. Radiation
4. All of these

Thermal energy can be transferred by:

1. Conduction
2. Convection
3. Radiation
4. All of these

When light changes in direction when entering one transparent medium to another is known as?

1. Reflection
2. Diffraction
3. Refraction
4. Absorption

Rainbow is formed due to:

1. Emission of light
2. Absorption of light
3. Refraction of light
4. Transmission of sound