Images, mirrors and lenses Flashcards
A real image is where
the light from the object comes together to form an image on a screen.
A virtual image is when
the rays are diverging, so the light from the object appears to be coming from completely different place.
When you look in the mirror, what sort of image do you see?
virtual, because the object appears to be behind the mirror
To describe an image properly, you need to say 3 things, what?
- How big it is compared to the object.
- Whether its upright or inverted.
- whether its real or virtual.
What is the law of reflection?
angle of INCIDENCE= angle of REFLECTION
Refraction of light
is when the waves of light change direction as they enter a different medium.
What is refraction caused by?
The change in speed of the waves due to the change in density.
3 points for a ray diagram of a plane mirror
- The image is the same size as the object
- It is as far behind the mirror as the object is in front.
- formed from diverging rays so is virtual.
Concave
curved mirror, shiny on the inside, light shining on it will diverge
what is the centre of the mirrors surface called?
Vertex
What is halfway between the vortex and the centre of curvature C?
Focal point, F
How do you draw a ray diagram for an image in a concave mirror?
- An incident ray parallel to the axis will pass through the focal point when its reflected.
- An incident ray passing through the focal point will be parallel to the axis when its reflected.
How do you draw a ray diagram for an image in a concave mirror?
- An incident ray parallel to the axis will reflect so that the reflected ray seems to come from the focal point.
- An icident ray that can be extended to pass through the focal point will be parallel to the axis when its reflected.
The image in a convex mirror is always…
virtual, upright, smaller than the object and behind the mirror, closer than F.
What does a ray bend toward as it enters a denser medium?
the normal
Different wavelengths of light refract by
different amounts
Why doesn’t a rectangular prism produce a rainbow effect like a triangular prism?
The boundaries are parallel so the rays bend back again by the same amount as they leave so they meet up again and white light emerges.
What is a converging lens?
A lens which is convex
what is a diverging lens?
A lens which is concave.
What are the 3 rules for refraction in a converging lens?
- An incident ray parallel to the axis refracts through the lens and passes through the focal point on the other side.
- An incident ray passing throough the focal point refracts through the lens and travels parallel to the axis.
- An incident ray through the centre carries on in the same direction.
What are the 3 rules for refractio in a diverging lens?
- An incident ray paralell to the axis, refracts and travels in line with the focal point( appearing to come from it)
- An incident ray towards F refracts and travels parallel to the axis.
- An incident ray passing through the centre carries on in the same direction.
What sort of image does a diverging lens produce?
virtual, upright, smaller than object, same side of lens to object sort of image.
What sort of lenses do magnifying glasses use?
Convex
For a magnifying glass to magnify, the object mustbe..
Closer to the lens then the focal point.
What sort of image does a magnifying glass produce?
Virtual image.
What is the formula for magnification?
Magnification= image height/ object height
What sort of image is an image on a film?
A real image.
Why is the image on a film smaller?
the object is a lot further away from the focal length of the lens.
