Electromagnetic Spectrum

Question 1

Name everything on the EM Spectrum in order.

(lowest to highest frequency)

Answer 1

Radio Waves
Microwaves
Infrared radiation
Visible light
Ultra Violet radiation
X-Rays
Gamma Rays

Question 2

What is the speed of the EM waves in a vacuum?

Answer 2

3 x 10⁸ m/s

Question 3

What are gamma rays used for and what are the associated risks?

Answer 3

uses: food preservation, medical imagery, astronomy and sterelisation
risks: can penetrate living tissues and cells, leaving them damaged.

Question 4

What are X-Rays used for and what are the associated risks?

Answer 4

uses: airport baggage checks, medical imagery, killing cancerous cells.
risks: can cause ionisation of cells, leaving them damaged.

Question 5

How are some of the safety hazards of working with X-Rays overcome?

Answer 5

• Minimum exposure.
• Shielding, often with metal or lead to prevent damage from X-Rays.

Question 6

What is Ultra Violet light used for and what are the associated risks?

Answer 6

Uses: detecting fake bank notes, air purification, forensic photography, medical therapy and disinfection.
Risks: skin burns, skin cancer and cataract formations in the eye

Question 7

What is Infrared radiation used for and what are the associated risks?

Answer 7

Uses: Remote controls, motion detection intruder alarms
Risks: If emmited from a high intensity source, it can cause skin burns.

Question 8

What are microwaves used for and what are the associated risks?

Answer 8

Uses: Heating up food, satellite comunnication/telecommunication
Risks Exposure to high levels of microwaves can cause a painful skin burns

Question 8

What are radiowaves used for and what are the associated risks?

Answer 8

Uses: radio and TV communication
Risks: Exposure to high intensity radio waves can cause internal heating of tissues

Question 9

How can EM Waves be produced?

Answer 9

• through electrical current
• through changes in atoms

Question 10

Why is visible light used in Fibre Optic Cables?

Answer 10

Visible light can be totally internally reflected, and therefore can transmit information along optical fibres without getting lost.

Question 11

What happens when light hits an object?

(Of any wavelength on the EM Spectrum)

Answer 11

It is either absorbed, reflected, refracted or transmitted.

Question 12

What determines if an object is transparent, translucent or opaque?

Answer 12

Transparent - it will transmit light without scattering the rays
Opaque - Light is either reflected or absorbed, none is transmitted.
Translucent - They transmit light but scatter the rays

Question 13

How does specular reflection occur?
And how does diffuse reflection occur?

Answer 13

Specular - Light bounces off off a SMOOTH surface and in a single direction PERPENDICULAR to that of which it came from
Diffuse - Light bounces of a ROUGH surface in many directions, as the DIFFERENT LEVELS of the rough surface cause it to reflect at VARYING DIRECTIONS

Question 14

Why does a yellow mug appear yellow?

Answer 14

The mug absorbs all the other colors within visible light and reflects only yellow.

Question 15

Why does any white opaque object appear white?

Answer 15

All the wavelengths (of visible light) have been reflected equally, so it appears a combination of all the colours in visible light - white.

Question 16

Why does any black opaque object appear black?

Answer 16

All the wavelengths (in visible light) have been equally
absorbed, therefore it looks black.

Question 17

What is the critical angle for most glass?

Answer 17

42°

Question 18

How does internal reflection work?

Answer 18

Light rays pass through a more dense to a less dense medium, and is therefore both reflected and refracted.

The light slows down when entering the more dense medium and moves towards the normal. The light speeds up when entering the less dense medium and moves away from the normal

Question 19

What happens if light passes through the critical angle?

Answer 19

The light will be refracted between the boundary of both mediums, and will also be reflected out.

Question 19

What is total internal reflection?

Answer 19

When the light coming in exceeds the critical angle, no light is refracted and all the light is reflected.

Question 19

Why is a body at a constant temperature?

Answer 19

The body emits radiation at the same rate that it absorbs it.

Question 20

Explain how the greenhouse effect works

Answer 20

1. The sun emits radiation, notably visible light
2. This radiation reaches earth, where some is absorbed, and some is re-emitted back into the atmosphere as infrared radiation.
3. The atmosphere, which contains greenhouse gasses (e.g, CO₂ and H₂O) re-emit this radiation in all directions, including the direction of earth.
4. That increaces the temperature of earth, keeping it habitable.

Question 21

What do waves transfer?

Answer 21

Energy and Information NOT matter.

Question 22

What lens produces virtual images, and what lenes produces real images?

Answer 22

Convex/Converging lenses produce real images and virtual images
Concave/Diverging lenses produce virtual images

Question 23

In what direction does light bend when going from air to glass?
And in what direction does light bend when going from glass to air?

Answer 23

Air to Glass - Towards the normal
Glass to air - Away from the normal