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