2 types of mirror
Convex (curves outwards) and Concave (curves inward)
Concave and convex mirror are also knwon as
Concave = converging mirror
Convex = Diverging mirror
2 types of images formed by mirror
Real image:
Inverted
Formed as a result of two or more light rays intersecting at a point
Virtual image:
Imaginary place where the image would form if the two or more light rays intersected
Upright
Centre of curvature
Midpoint of the sphere frm which the mirror has been obtained
Radius of Curvature
Radius of the sphere from which the mirror has been obtained
Optical centre
Midpoint of the reflecting surface
Principle axis
Imaginary line joining the Centre of curvature and the optical centre
Principle Focal point
Point located on the principle axis, in the middle of the optical centre and the centre of curvature, through which all reflected light ways pass through provided the incident ray are parallel to the principle axis
Focal length
Distance betwen the Focal Point and the Optical centre
Cases of incident light rays in concave
- Incident light ray pases parallel to the principle axis, then the reflected light ray goes through the Focal point
- Incident light ray pases through the focal point, then the reflected light ray pases parallel to the principle axis
- Incident light ray pases through the centre of curvature, then the reflecting light ray retraces the same path and goes through the centre of curvature as well
Concave mirror image formation: Object at Infinity (very high distance compared to focal length)
Image will be formed at Focal point
Nature = Real, inverted, point sized
Concave mirror image formation: Object at beyond Centre of curvature
Image will be formed between centre of curvature and Focal point
Nature = Real, Inverted, diminished in size
Concave mirror image formation: Object at Centre of curvature
Formed at centre of curvature itself
Nature = Real, Inverted, Same size
Concave mirror image formation: Object at between centre of curvature and focal point
Image will be beyond centre of curvature
Nature = Real, Inverted, enlarged
Concave mirror image formation: Object at Focal point
Image will be formed at infinity
Nature = Real, Inverted and highlighy enlarged
Concave mirror image formation: Object at between focal point and optical centre
No real image will be formed.
Virtual image will be formed on the other side of the mirror assuming the direction of incident lines
Nature = Virtual, Upright, Enlarged
how does a refracting telescope work?
An objective lens captures all the light rays coming from the planet and focuses it at the focal length’ (F’) of the objective convex lens
Another convex lens is used as the eyepiece. The focal length of the eyepiece meets the focal length of the objective lens. The real and inverted image formed by the objective lens is used as the object for the eyepiece. Hence it forms a highly enlarged image. The inverted-inverted cancel each other out to show us the upright image towards our eyes.
how does a reflecting telescope work?
Light rays hit a parabolic concave mirror with bounce of the mirror and hit a plain mirror at an angle. This plain mirror focuses the light for our eyes.
The lights cross at the focal length of the eyepiece and gets delivered to the eyepiece lens, which is a convex lens.
The eyepiece delivers the light parallel to our eyes, allowing for upright image viewing and better image quality
cases of incident and reflected rays in convex mirrors
- Incident light ray parallel to the principle axis, then the reflected light ray passes through focal point on the other side
- Incident light ray pases through the focal point, reflected light ray passes parallel to the principle axis on th eother side of the mirror
- Incident light raya passes through the optical centre, the reflected light ray passes through without any deviation
Convex mirror image formation: Object at infinity
Image is also at focal point
Nature = Real, Inverted and point sized
Convex mirror image formation: Object at beyond focal length
Image at between focal point and 2F
Nature = Real, Inverted, Diminished
Convex mirror image formation: Object at 2F
Image formed at 2F on the other side of mirror
Nature = Real, Inverted, Same size
Convex mirror image formation: Object at between Focal point and 2F
Image at beyond 2F on other side of mirror
Nature = Real, Inverted and enlarged
Convex mirror image formation: Object at Focal point
Image at inifnity on other side of mirror
Nature = Real, Inverted, Highly enlarged
