Question

Can someone please help me ik that question 2) is d. and that question 4) is c.

Answer 1

1) a) Mechanical waves require a medium, electromagnetic waves do not

2) d) A single pulse tone is sent from an underwater speaker through a pool of water and the water molecules are compressed in the direction of the wave

3) a) can transfer energy from one point to another

4) c) in the same direction

5) a) a light bulb

6) b) crest and trough

Explanation:

1)

Waves are periodic disturbance of space that carry energy without carrying matter.

Waves are classified into two types:

• Mechanical waves: these waves are produced by the periodic oscillations of the particles in a medium, which can travel back and forth along the direction of propagation (longitudinal waves) or perpendicular to the direction of propagation (transverse waves). Examples of mechanical waves are sound waves.
• Electromagnetic waves: these waves consist of oscillations of the electric and magnetic fields, which vibrate in a plane perpendicular to the direction of propagation of the wave (transverse waves). These waves are the only waves that can travel through a vacuum.

Therefore, the correct answer is

a) Mechanical waves require a medium, electromagnetic waves do not

2)

Waves are classified into two types depending on the direction of their oscillation:

• Transverse waves: in these waves, the direction of the oscillation is perpendicular to the direction of propagation of the wave. For instance, if the wave travels forward, the oscillation occurs up and down or left-right. Examples of transverse waves are electromagnetic waves.
• Longitudinal waves: in these waves, the direction of the oscillation is parallel to the direction of propagation of the wave. So, if the wave travels forward, the oscillation of the particles occur back-and-forth.

Therefore, the option that describes a longitudinal wave is

d) A single pulse tone is sent from an underwater speaker through a pool of water and the water molecules are compressed in the direction of the wave

3)

Waves are periodic disturbance of the space that carries energy, but without carrying matter.

This means that all waves transfer energy from one point to another (depending on the direction towards which they travel), however while doing so, matter is not carried towards the final point.

In fact, while the wave travels, matter only vibrate around their equilibrium position, but it does not travel alongside with the wave.

On the other hand, energy is carried together with the wave. This is valid for any type of wave, so both mechanical and electromagnetic waves.

So, the correct option is

a) can transfer energy from one point to another

4)

A compression wave is another term for "longitudinal wave".

As we said before, a longitudinal wave is a wave in which the particles in the medium oscillate in a direction parallel to the wave (back and forth).

Examples of longitudinal waves are:

- Sound waves (particles of the wave oscillate back and forth along the direction of propagation)

- Waves on a slinky (the oscillation occurs back and forth)

Therefore, the correct option for a compression wave is

c) in the same direction

5)

As we said in part 1), there are two types of waves:

• Mechanical waves, which do need a medium in order to propagate
• Electromagnetic waves, the only type of waves that can travel through a vacuum

Electromagnetic waves are oscillations of the electric and magnetic field in a direction perpendicular to the direction of propagation of the wave. In a vacuum, they travel at a speed of

$c=3.0\cdot 10^8 m/s$

Electromagnetic waves are classified into different types, according to their frequency/wavelength. For instance, we have radio waves, microwaves, x-rays, ultraviolet, visible light..

Every hot objects, such as a light bulb, emit electromagnetic waves. Therefore, the correct option is

a) a light bulb

6)

Electromagnetic waves are transverse waves, which means that the direction of oscillation of the wave (electric and magnetic field) is perpendicular to the direction of propagation of the wave.

For a transverse wave, the wave oscillates up and down, therefore we can define:

- A point where the wave has the maximum positive displacement from the equilirium position - this is called crest

- A point where the wave has the maximum negative displacement from the equilibrium position - this is called trough

Therefore, the correct option is

b) crest and trough