Topic 5 - Light & EM Spectrum

Are EM waves transverse or longitudinal waves?

Transverse

Where do all EM waves travel at the same speed?

Vacuum

If an EM wave has a higher frequency, does it transfer more or less energy?

More energy

List the EM spectrum in order of decreasing wavelength

Gamma, X - Ray, Ultraviolet, Visible Light, Infrared, Microwave, Radiowave

List the EM spectrum in order of increasing frequency

Gamma, X - Ray, Ultraviolet, Visible Light, Infrared, Radiowave, Microwave

List the EM spectrum in order of increasing wavelength

Radiowave, Microwave, Infrared, Visible Light, Ultraviolet, X - Ray, Gamma

List the EM spectrum in order of decreasing frequency

Radiowave, Microwave, Infrared, Visible Light, Ultraviolet, X - Ray, Gamma

Does the dangers associated with the EM spectrum increase as frequency decreases or increases?

Increases

Does the dangers associated with the EM spectrum decrease as frequency decreases or increases?

Decreases

Which EM wave has the highest frequency?

Gamma

Which EM wave has the lowest frequency?

Radio wave

Which EM wave has the longest wavelength?

Radiowave

Which EM wave has the shortest wavelength?

Gamma

Which EM wave is the least dangerous?

Radio wave

Which EM wave is the most dangerous?

Gamma Rays

Are radio waves dangerous? Why?

No because they don’t transfer much energy, and therefore only cause a small rise in temperature.

They are also transmitted throughout the body without being absorbed.

Are micro waves dangerous? Why?

Slightly as they can be absorbed, causing internal heating on body tissues.

Are infrared dangerous? Why?

Yes as it is mainly reflected or absorbed, causing burns due to lots of heat and skin cancer if a person is excessively exposed.

Is visible light dangerous? Why?

No although it can damage the retina sometimes.

Is ultraviolet dangerous? Why?

• Yes as it’s highly ionising so can ionise atoms in our cells and be absorbed by the skin. Leads to damaged cells and DNA mutation (cancer).

• Can lead tos skin cancer when absorbed or skin aging prematurely.

• Can damage yes, leading to blindness whilst visible light only damages the eyes, no blindness.

Are x rays dangerous? Why?

Highly ionising so can ionise atoms in our cells and be absorbed by the skin. Leads to damaged cells and DNA mutation (cancer).

Are gamma rays dangerous? Why?

• Yes as it’s highly ionising so can ionise atoms in our cells and be absorbed by the skin. Leads to damaged cells and DNA mutation (cancer).

• Overexposure can lead to radiation sickness.

• Can lead tos skin cancer when absorbed or skin aging prematurely.

• Can damage eyes by causing cataracts.

How can we protect ourselves from EM waves?

• Reduce exposure.

• Shielding like standing behind screens during x - ray.

• Suncream to reduce exposure to UV.

• Wear eye protection from UV and visible lights.

• Microwave have covers and coating to shield people.

How does our skin naturally respond to UV?

Turns darker (tan) as darker skin absorbs more so less reaches deeper tissues.0

How are radio waves produced?

By electrons oscillating in electrical currents with alternating currents.

1. Charges/electrons oscillate, meaning they continually change direction and flow up and down in the Ariel. This creates radio waves in a transmitter.

2. Transmitted radio waves reach a receiver to be absorbed.

3. Energy carries by waves is transferred to the electrons in the material of the receiver.

4. These electrons oscillate in an electrical circuit, generating an alternating currents with the same frequency as the radio waves generated.

How are x ray waves produced?

• Electrons move energy levels. In lower energy levels, they absorb energy.

• Electrons move to higher ones and when they go back down, they lose energy via radiation.

• Electrons need a large amount of energy so they emit x ray radiation of high energy/frequency.

What are the uses of radio waves?

• Bluetooth

• TV and FM radio

• Communications

• Satellite transmissions

What are the uses of micro waves?

• Satellite communcations

• TV

• Cooking

What are the uses of infrared radiation?

• Infrared cameras

• Thermal imaging

• Infrared sensors

• Cooking

• Heaters

• Transfers information e.g. TV remote and sending files.

What are the uses of visible light?

• Photographic film

• Digital camera

What are the uses of ultraviolet?

• Tanning machines

• Security inks/pens

• Detecting bank notes

• Security marking

• Fluorescent lights

What are the uses of x rays?

• Radiographers in hospitals detect broken bones via medical x ray scanners.

• AirPort security scanners.

What are the uses of gamma rays?

• Sterilise medical instruments and food.

• Tracers.

• Treat/Killcancer.

Describe examples of EM waves transferring energy.

• Radio waves in communication.

• Microwaves in cooking and communication.

• Infrared in cooking, thermal imaging and TV remote.

• Ultraviolet in detecting banks notes, disinfecting water, skin cancer, security marking and fluorescent lamps.

• X rays in observing internal structures, security scanners and medical x rays.

• Gamma in sterilising food or equipment and detecting cancer/its treatment.