Lenses Flashcards
What type of lens is a convex lens
Converging lens (The rays of light after the lens get closer)
Describe the principle of focus, F on a converging lens
If the rays of light coming into the lens are parallel rays then the point they converge it called the principle of focus
Where is the focal length
It is the distance from the principle of focus to the centre of the lens.
What is the method of measuring the focal length of a convex lens
- Set up apparatus as shown in diagram (Metre ruler, White screen, Convex lens, Lens holder)
- Move the lens slowly away from screen until a focused image of a distant object forms on the screen.
- Measure the distance from the screen to the centre of the lens using a ruler (focal length)
- Repeat and take average
Why is light from a distant object used to form an image on a screen using a convex lens
Light from a distant object is used so the rays will enter the lens parallel to eachother
If you use a thicker lens how will the focal length be compared to the less thicker lens in a convex lens
The focal length will decrease
What type of lens is a concave lens
a diverging lens (The rays of light after the lens get further apart)
Describe the principle of focus, F on a diverging lens
If the rays of light coming into the lens are parallel rays then the point from which they appear to come from is the Principle of focus.
What is a virtual image
An image that cant be focused onto a screen
What is a real image
An image that can be focused onto a screen
What does diminished mean
The image gets smaller or less
What does inverted mean
The image is upside down or in the opposite position
What are the uses of lenses
- A camera
- A projector
- A magnifying glass
How does a camera focus to take pictures of objects at different distances
The lens is moved forwards and backwards from the focal length so a focus image is formed on the film
What type of lens do our eyes have
Convex lens/ Converging
