The Human Eye
This part of the eye controls the amount of light entering the eye.
iris
This quantity represents the distance from the lens to the object.
object distance (dâ‚’)
A ray passing through the optical centre of a lens follows this path.
it continues in a straight line
A camera forms this type of image on its sensor.
real image
This phenomenon causes a pencil to appear bent in water.
refraction
This structure changes shape to focus light onto the retina.
the lens
Using the lens equation, determine the focal length when an object and image are both 20 cm from the lens.
10 cm
A ray parallel to the principal axis of a convex lens refracts through this point.
the focal point
This device uses lenses to allow scientists to view tiny structures.
microscope
Light travels fastest in this medium.
vacuum
Images are detected by this light-sensitive layer at the back of the eye.
the retina
A positive focal length indicates this type of lens.
convex lens
How many principal rays are usually required to locate an image in a ray diagram?
two
Astronomers use this optical instrument to observe distant objects in space.
telescope
A convex lens forms an image that is upright and enlarged. Where is the object located?
inside the focal length
A person who is nearsighted can see nearby objects clearly but has difficulty seeing these.
distant objects
An object is placed 30 cm from a lens and forms an image 15 cm away. Calculate the focal length.
10 cm
An object placed beyond the focal point of a convex lens produces this type of image.
real image
A magnifying glass uses a this type of lens to magnify nearby objects.
Convex lens
A student moves an object farther away from a convex lens. Predict what happens to the image size.
image becomes smaller
Explain why the image formed on the retina must be processed by the brain.
because the image formed on the retina is inverted
Why is the focal length considered a property of the lens rather than the object?
because it depends on the lens shape and material, not the object's position
Explain why ray diagrams are useful in optics.
because they predict image location, size, and orientation
Explain why microscopes require more than one lens.
because multiple lenses provide greater magnification and image clarity
Compare a real image and a virtual image.
a real image can be projected onto a screen, while a virtual image cannot