Compare the properties of mechanical waves and electromagnetic

waves. How do their mediums of propagation and the requirement

for a medium differ?

Waves transport energy, not matter!!

- Mechanical waves: require a medium to travel (air, water, solids)

Electromagnetic: electric and magnetic fields which interact with charged

particles (electrons and protons) and make them oscillate/accelerate. This
affects the particles trajectory. Charged particles: generate electric fields.
Photons cause acceleration of the particle, leading to the creation of a
magnetic field. The magnetic field and electric field disturb each other,
causing the disturbance to propagate in the form of an electromagnetic wave.
The amount of acceleration and oscillation determines the intensity of the
electromagnetic wave.

- don’t require a medium

- can travel through empty space
- are all transverse waves
- types are all in the electromagnetic spectrum

RAGING MARTIANS INVADED VENUS USING X RAYS GUNS

- in a vacuum, they always travel at the speed of light but in a medium,

the speed is reduced depending on the medium’s refractive index
- When changing medium, the electromagnetic wave is partly refracted
and partly reflected

 Visible light, ultraviolet and x rays emitted by electrons dropping down

energy levels
 Gamma rays caused by radioactive decay
 Infrared by bonds who are holding molecules together vibrate

Black-Body Radiation: All objects emit electromagnetic radiation based on

their temperature. This emission is called black-body radiation. The spectrum
of the emitted radiation depends on the temperature of the object. It means
that all objects that have a temperature above 0 K emits electromagnetic
waves

How does the functioning of mirrors explain the ability of surfaces to

refract light?

Refraction refers to the bending of light, which occurs when light changes
speed as it passes through different media. Denser materials reduce the
speed of light, causing it to bend.

Smooth Surfaces: Reflect light at precise angles, creating clear reflections.

Rough Surfaces: Scatter light in various directions, leading to diffuse

reflections.

Electronic transition: absorption of a photon by a particle causes electrons to

move from low to high energy

When light travels through non-vacuum materials, photons interact with the
atoms, causing the atoms' electrons to vibrate. This vibration leads to the
emission of new photons, which travel at the same speed as the original
photons. The movement of these charged particles generates magnetic
fields, disturbing the electric field and creating induced magnetic waves. Our
eyes perceive a combination of the original light and the induced light,
resulting in constructive and destructive interference. This interference
creates a wave that travels with a slower effective velocity than light in a
vacuum.

Electric fields in blue, Magnetic fields in red

Discuss the concepts of reflection, refraction, and transmission.

Reflection: Reflection occurs when a wave, such as light, bounces off the
surface of a material and changes direction while staying in the same
medium.

Refraction: Refraction is the bending of a wave as it passes from one medium

to another with a different density, causing a change in speed.
Transmission: occurs when a wave passes through a material without being
absorbed or reflected.

During an experiment, two samples are heated to the same high

temperature: one sample is a piece of aluminum (a metal) and the
other is a piece of ceramic (a non-metal). The experiment aims to
observe the emission of electromagnetic radiation from both
samples. The following observations are made:

1. The aluminum sample emits visible light more quickly than the
ceramic sample.
2. Both samples eventually emit visible light once they reach the
high temperature.

Based on these observations, explain the differences in the thermal

properties of metals and non-metals that lead to these results.

Metals like aluminum have high thermal conductivity due to the presence of
free electrons. These electrons can move easily throughout the material,
transferring energy efficiently and allowing the metal to heat up quickly and
uniformly. This rapid heat distribution enables metals to reach the high
temperatures required for visible light emission faster than non-metals. Non-
metals like ceramic have lower thermal conductivity because they lack free
electrons. Heat is transferred primarily through lattice vibrations (phonons),
which is a less efficient process. As a result, non-metals take longer to heat
up uniformly to the same temperature, delaying the emission of visible light
compared to metals.

Describe the difference between transverse and longitudinal waves.

Provide examples of each type and explain how particle motion
differs in each case

Transverse waves: oscillate perpendicularly to the

direction of energy transfer,

String waves, water waves, electromagnetic waves

Longitudinal waves: oscillation parallel to the direction of energy transfer

Sound waves, earthquake p waves

Explain what polarization of light is and how it can be achieved.

Discuss one practical application of polarized light

 Absorption: When an atom or molecule absorbs a photon (a particle of

light), an electron can move from a lower energy level to a higher energy
level. This is known as an electronic transition.

Example: In the photoelectric effect, photons of sufficient energy can cause

electrons to be ejected from a metal surface.

 Emission: Electrons can also move from a higher energy level to a lower
one, emitting a photon in the process. This is the basis of phenomena like
fluorescence and phosphorescence

Usually, when electromagnetic waves propagate, they have a chaotic shape

(non-polarized).

But controlled vibration can be achieved when electrons are moving in a

controlled shape.

3 types of movement:

- Rectilinear
- Elliptical
- Circular

Our eyes are only sensible to the intensity of the electromagnetic wave but
not of the direction of the waves

Discuss the relationship between the amplitude of a wave and the

energy it carries. How does the energy of a wave change if its
amplitude is tripled?

The energy carried by a wave is directly related to the square of its amplitude. In
mathematical terms, if E represents the energy and A represents the amplitude, the
relationship can be expressed as:
E ∝ A²

This means that if the amplitude of a wave increases, the energy it carries increases
proportionally to the square of the amplitude.

Therefore, if the amplitude of the wave is tripled, the energy it carries increases by a
factor of 9. This significant increase in energy illustrates the strong dependence of wave
energy on the amplitude.

Analyze how the speed of sound changes in different media such as

air, water, and steel. Explain why sound travels faster in solids than
in liquids or gases.

The speed of sound increases in high density materials.

The bulk modulus is a measure of a material's resistance to uniform

compression. Solids have a much higher bulk modulus than liquids and gases,
meaning they are less compressible and can transmit sound waves more
efficiently. This high resistance to deformation allows sound waves to
propagate more quickly through the material.

An ambulance siren emits a sound at a frequency of 800 Hz. If the

ambulance is moving towards an observer at a speed of 30 m/s and
the speed of sound in air is 343 m/s, calculate the observed
frequency of the sound.

To calculate the observed frequency of sound when the source is moving towards the
observer, we use the Doppler effect formula for sound. The formula for the observed
frequency (f′f′) when the source is moving towards a stationary observer is:
PHOTOELECTRIC EFFECT QUESTION