Light and electromagnetic waves (separate science) Flashcards
What are the safety precautions that somebody needs to take if they are working with x-rays?
Wearing a flim badge: This detects the levels of radiation a person has been exposed to. If they have been exposed to too much then they cannot work with radiation for a period of time
Safety screens: Workers will stand behind a safety screen when they are using the radiation. The screen stops the radiation from getting to them
Explain how an X-ray image is formed
X-rays are generated in an x-ray tube and pass through the pateint to an x-ray film. Moden x-ray films are an electronic device called a Charge Coupled Device (CCD) which can detect x-rays.
The X-rays can pass through soft tissue (skin and muscle) to hit the film, but cannot pass through the bone. This creates a ‘shadow’ of the bone on the screen.
The bones look white on x-ray because the film starts white, and turns black if an x-ray hits it
Explain how an x-ray tube generates x-rays
In an x-ray tube, a wire is heated up which releases electrons. The electrons are then accelerated by an electric field and collide with a metal anode.
When the x-rays collide with the anode they slow down suddenly. The energy transferred away from the kinetic energy store when they slow down is relaeased as an electromagnetic wave (an x-ray)

What is a contrast media?
How is it used to help with medical x-rays?
A contrast media is a substance that x-rays cannot pass through.
It is injected into the body to highlight certain organs and structures (such as the kidneys and bladder) so that they can be seen on x-ray
Which two factors affect the dose of x-rays recieved by a patient?
- The intensity of the x-rays (how powerful they are)
- The length of time they are exposed to the radiation for
What is a Sievert?
How many milli Sieverts are in a Sievert?
The Sievert is the unit of biological radiation exposure. It tells you the dose of radiation you have been exposed to.
There are 1000 mSv in 1 Sv
What is the difference between an X-ray scan and a CT scan
An x-ray scan sends a beam of x-rays through the patient to hit a film. This creates a single 2D image.
A Computerised Tomography (CT) scan uses a beam of x-rays which spiral round the patient. This can be used to construct a 3D image in slices of the inside of the body.

What is the difference between the doses of radiation a person recieves in a CT scanner compared to a normal X-ray
The patient recieves a much higher does in a CT scanner than they do if they have a normal x-ray taken.
What is the law of reflection?
The law of reflection states that the angle of incidence is equal to the angle of reflection.

What is the difference between a real image or a virtual image?
A real image is an image that can be projected on a screen. This is becuase the device causes the rays of light to cross.
A virtual image is an image that cannot be projected onto a screen. This is because the device causes the rays of light to diverge (spread out)
What are the characteristics of the image formed by a mirror
- Lateral inversion - Things on the left appear to be on the right. Things on the right appear to be on the left
- Virtual image - the image cannot be projected on a screen
Draw a ray diagram showing the reflection of a light ray at an angle of incidence of 45o

What are the two types of reflection?
Which of these types will form a clear image when light reflects off it?
Specular reflection: All light rays which are parallel will be reflected in the same direction. This occurs if the surface is smooth
Diffuse reflection: Parallel light rays are not reflected in the same direction. This is becuase the surface is rought
If specular reflection occurs a clear image will be formed. If diffuse reflection occurs then a clear image is not formed.
Explain how to investigate the law of reflection
- Set up a mirror on a piece of paper.
- Draw a normal to the mirror on a piece of paper
- Dse a ray box to shine a ray of light at a mirror. measure the angle of incidence and the angle of reflection
- Change the angle of incidence by 5o and repeat the experiment
- Do this for at least 5 angles of incidence and observe the pattern created
Complete this ray diagram to show where the image will appear


Explain how this image shows that a mirror produces a virtual image

The solid lines represent the actual light rays. As the real light rays do not cross it does not form an image that can be shown on a screen.
This means that it is a virtual image.
When investigating refraction, explain how to meausre the angle of incidence or angle of refraction
angles of incidence and refraction are measured between the light ray and the normal
Draw a ray diagram to show the refraction of light at a boundary. The angle of incidence is 50o and the angle of refraction is 30o

Explain why ligh disperses when it passes through a prism
White light is made of all of the colours of light. Different colours of light refract by different amounts. Red light refracts the most and violet light refracts the least.
The refraction causes the light to spread out from each other

Explain how to investigate how the angle of incidence affects the angle of refraction
- Set up the equipment as shown in the diagram. Make sure the block is on a piece of paper with the normal drawn on it
- Shine a ray of light from the ray box into the block and mark on the paper the incident and refracted ray.
- measure the angle of incidence and the angle of refraction
- Increase the angle of incidence by 5o and measure the angle of refraction
- repeat the experiment increasing the angle of incidence by 5o each time. take at least 5 readings
- plot a graph of the angle of incidence against the angle of refraction.
Explain the water in a swimming pool does not look as deep as it actually is
The light moving from the floor of the pool to the surface is refracted when it breaks the water. This bends it away from the normal so the light becomes more horizontal. The result is that the floor seems to be higher up,

Explain why some colours of light refract more than others
How does this explain light dispersal by a prism?
Different colours of light will travel at different speeds when passing through a medium that is not a vacuum
The longer the wavelength of the ligh, the greater the change of speed when it passes from one medium to another. If there is a greater change of speed, then there will be the largest amount of refraction
As red light has the longest wavelength it is refracted the most by a prism. As violet light has the shortest wavelength it refracts the least. This means that the light spreads out as they all leave the prism at different angles
What is the visible light spectrum?
The visible light spectrum is a continuous range of wavenegths that can be detected by the human eye. It ranges from a wavelengh of 400nm (violet light) to 750 nm (red light)
Explain how objects can have a colour
Objects will reflect some colours of light and absorb others. Coloured objects will absorb all colours of light apart from the colour that it is, which it reflects back.
For example, with a red object, white light will hit it which contains all the colours in the visible spectrum. All of the colours in the white light is absorbed aside from the red light, wich is reflected back and detected by the eye. This means that the eye sees it a red







