Unit 3 - Energy transfers 2

What type of radiation does not require a medium for transfer?

• Ultraviolet radiation

• Infrared radiation

• Gamma radiation

• Visible light

Answer explanation

Infrared radiation is a type of electromagnetic radiation that can travel through a vacuum, meaning it does not require a medium for transfer. This distinguishes it from other forms like sound, which do require a medium.

Which type of body is the best absorber and emitter of radiation?

• Reflective bodies

• Transparent bodies

• Dull bodies

• Shiny bodies

Answer explanation

Dull bodies are the best absorbers and emitters of radiation because they have a rough surface that allows them to absorb and emit energy effectively, unlike shiny or reflective bodies that tend to reflect radiation.

What is the best reflector of radiation?

• Black bodies

• White bodies

• Opaque bodies

• Dull bodies

Answer explanation

White bodies are the best reflectors of radiation because they reflect all wavelengths of light equally, unlike black bodies which absorb all radiation. This makes white bodies ideal for reflecting radiation effectively.

What happens to the infrared radiation emitted as temperature increases?

• It decreases

• It remains constant

• It becomes visible

• It increases

Answer explanation

As temperature increases, the energy of the emitted radiation also increases, leading to a rise in the amount of infrared radiation. Therefore, the correct answer is that it increases.

What is work defined as in physics?

• Force times time

• Force times distance

• Energy times distance

• Mass times acceleration

Answer explanation

In physics, work is defined as the product of force and the distance over which it acts. Therefore, the correct answer is 'Force times distance', as it accurately represents how work is calculated.

What does gravitational potential energy convert to when a ball is dropped?

• Thermal energy

• Nuclear energy

• Kinetic energy

• Chemical energy

Answer explanation

When a ball is dropped, its gravitational potential energy is converted into kinetic energy as it accelerates towards the ground. This increase in kinetic energy is due to the conversion of potential energy during the fall.

What is the formula for kinetic energy?

• E_k = mv

• E_k = Fd

• E_k = mgh

• E_k = 1/2 mv^2

Answer explanation

The correct formula for kinetic energy is E_k = 1/2 mv^2, where m is mass and v is velocity. This formula shows that kinetic energy is proportional to the mass of an object and the square of its velocity.

What does power measure in physics?

• Energy transferred per unit time

• Force applied per unit distance

• Work done per unit mass

• Speed of an object

Answer explanation

In physics, power measures the rate at which energy is transferred or converted. It is defined as energy transferred per unit time, making the correct choice 'Energy transferred per unit time'.

What happens to a lamp with greater power?

• It is dimmer

• It transfers less energy

• It is brighter

• It consumes less energy

Answer explanation

A lamp with greater power consumes more energy, which results in a higher light output. Therefore, it is brighter compared to lamps with lower power.

What is the formula for gravitational potential energy?

• E_p = 1/2 mv^2

• E_p = Fd

• E_p = mv

• E_p = mgh

Answer explanation

The formula for gravitational potential energy is E_p = mgh, where m is mass, g is the acceleration due to gravity, and h is height. This formula correctly represents the energy stored due to an object's position in a gravitational field.