Lenses Flashcards
How do lenses form images
By refracting light and changing its direction
What are the 2 main types of lenses
Concave and convex
What do concave lenses do to light
It causes … rays of … to spread outwards (d…)
It causes parallel rays of light to spread outwards (diverge)
What do convex lenses do to light?
It causes … of light … to the … to be brought together (c…) at the principle …
It causes rays of light parallel to the axis to be brought together (converge) at the principle focus
What is the axis
The line passing through the middle of a lense
What is the principle focus of a convex lens
Where … hitting the lens … to the axis all meet
Where rays hitting the lens parallel to the axis all meet
—>after the lens
What is the principle focus of a concave lens
Is the point where rays hitting the lens parallel to the axis appear to all come from
—>before the lens
—> if you draw the lines after the lense back they all meet at this point
What is the focal length
The … from the … of the lens to the principle …
The distance from the centre of the lens to the principle focus
3 rules for refraction in convex lenses
1. An incident ray … to the axis always meets at the … focus on the other side of the …
2.a … ray passing through the … focus refracts through the … parallel to the …
- A … ray going through the … of the lens carries on in the … direction
- An incident ray parallel to the axis always meets at the principle focus on the other side of the lens
2.a ray passing through the principle focus refracts through the lens parallel to the axis
- A ray going through the centre of the lens carries on in the same direction
3 rules for refraction in concave lenses
- An incident ray parallel to the axis refracts through the lens in line with the principle focus
2.a ray going through the lens towards the principle focus refracts through the lens parallel to the axis
- A ray going through the centre of the lens goes in the same direction
What is a real image
Where the … from an object comes together to form an … on a “…”
Where the light from an object comes together to form an image on a “screen”
What is a virtual image
Where rays … so light from the … appears to be coming from a … place
Where rays diverge so light from the object appears to be coming from a different place
Eg of real and virtual images
Real:
-image formed on the eyes retina
Virtual:
-a mirror
-a magnifying glass
Concave lenses always produce a …. Image
Virtual
What does a virtual image look like
-right way up
-smaller than the object
-on the same side of the lense as the object
What lenses are in magnifying glasses
Convex lenses
Can u project a virtual image onto a screen
No
Equation linking Magnification, actual size, and image size
I=AM
