P3.1 Flashcards
What are ultrasound waves?
Sound waves of frequency above 20000Hz.
What is a refractive index?
Refractive index, n, is a measure of how much a substance can refract a light ray.
What is an endoscope?
Device that looks inside patients body without cutting it open or when performing keyhole surgery. Contains bundles of optical fibres. Visible light can be sent along fibres by total internal reflection.
What’s a converging lens?
Focuses parallel rays to a point called principal focus.
What’s a diverging lens?
Makes parallel rays spread out as if they came from a point called the principal focus.
Which lens forms a real image?
Formed by converging lens if the object is further away than the principal focus.
When is a virtual image formed?
By diverging lens, and by a converging lens if the object is nearer to the lens that the principal focus.
What image is formed between a converging lens and F?
Virtual, upright, magnified and on the same side of the lens as the object.
What’s a magnifying glass?
A converging lens used to form a virtual image of an object.
In the eye what is the light focused on?
The retina by the cornea and the eye lens, which is a variable focus lens.
What’s a short- sighted eye?
An eye that can only see near objects clearly. We use a diverging (concave) lens go correct it.
What are X-rays used for?
To make images and CT scans. To destroy tumours around body surface
What’s a long- sighted eye?
An eye that can only see distant objects clearly. We use converging (convex) lens to correct it.
The higher the refractive index of glass used…?
(To make a corrective lens) the flatter and thinner the lens can be.
What’s a CT scanner?
Device that used X-rays to produce digital images of a cross- section through the body.
