Science Grade 8 Unit 3 Topic 4-5 Flashcards
What’s a concave lens?
Middle is thinner and flatter than the edges, causing light to spread out or diverge
What’s a convex lens?
Middle is thicker than the edges, causing light to come together or converge. It also causes parallel rays to converge
What lens does human eye have?
Humans have convex lens. It refracts light and focussed them.
What’s refraction?
It’s a change in the direction of a wave passing from one medium to another.
Near-sighted:
Your eye is too long, the image forms in front of the retina. You can’t see far. You need a concave lens.
Far-sighted:
Your eye is too short, the image hasn’t formed by the time it reaches the retina instead it forms behind the retina. You can’t see close. You’ll need convex lens.
What’s a diaphragm?
It’s a device that controls the aperture (the opening) of a lens or optical system, like a camera.
What’s an optical system?
Lenses, mirrors, lights sources, thin film, etc.
What’s a shutter?
It’s a device that limits the passage of light. It can let it more light by staying open longer.
What’s an aperture?
It’s the pupil in the eyes.
What’s ciliary muscle?
Controls the shape of the lens to ensure the image is focused on the retina.
What’s cornea?
It protects the eyes.
What’s iris?
Controls the amount of light entering; the coloured part of the eye.
What’s a pupil?
The hole through which light enters?
What’s an aqueous humour?
A watery liquid, providing support to the lens.
What is a lens?
Focuses light.
What a vitreous humour?
A clear liquid taking most of the room in the eye; provides support in the eye. (The white part).
What’s a retina?
Has light sensing cells and receives light and sends to the brain.
What is fovea (focal point)?
Where light focuses.
What’s an optic nerve?
Connect the eye to the brain.
What’s a refracting telescope?
The light from a distant object is collected and focussed by a convex lens called the objective lens. Second part is called the eyepiece lens, like a magnifying glass to enlarge the image.
What’s a reflecting telescope
It uses a concave mirror to collect rays of light from a distant object. The mirror is called the primary or o he give mirror. Form real image = magnified by the eyepiece lens.
Whats a reflecting telescope?
It uses a concave mirror to collect rays of light from a distant object. The mirror is called the primary or o he give mirror. Form real image = magnified by the eyepiece lens.
What’s a binocular?
Two refracting telescopes mounted side to side. The telescopes are shortened by placing glass blocks inside. It reflects back and forth inside a short tube. These prisms greatly reduce the distance between the two lenses by allowing the light Rey to be reflected several timee off their surfaces.
