Objects in a completely dark room cannot be seen because no light from them reaches the eyes. Objects outside may be seen if they are illuminated and light from them enters the room and eyes.
Regular reflection occurs from smooth surfaces and reflected rays remain parallel. Diffused reflection occurs from rough surfaces and rays scatter in different directions. The laws of reflection still hold at each point.
Polished table - regular mostly; chalk powder - diffused; cardboard - diffused; wet marble - regular mostly; mirror - regular; paper - diffused.
The angle of incidence equals the angle of reflection. The incident ray, reflected ray and normal at the point of incidence lie in the same plane.
Fix a white sheet on a board, place a plane mirror upright, draw a normal, and send a ray from a torch along a marked line. The reflected ray can be traced on the same sheet, showing all three lines lie in one plane.
(a) 2 m (b) left, left hand (c) large (d) fewer cones than rods.
- a. Always
- b. Sometimes
- c. Under special conditions
- d. Never
(a) Always.
- a. virtual, behind mirror and enlarged
- b. virtual, behind mirror and same size
- c. real at surface and enlarged
- d. real, behind mirror and same size
(b) virtual, behind the mirror and of the same size as the object.
Join three rectangular mirror strips with reflecting surfaces facing inward to make a triangular tube. Close one end with translucent paper and the other with clear glass/plastic, placing small coloured glass pieces inside.
A labelled eye sketch should show cornea, iris, pupil, lens, retina, optic nerve and eyelids. Light enters through cornea and pupil, is focused by the lens on retina, and signals go through the optic nerve.
Laser light is very intense and can damage the retina if it enters the eye.
Read in proper light, do not look at the sun or laser, keep books at a comfortable distance, wash eyes with clean water, eat vitamin A rich food, avoid rubbing eyes, and consult an eye specialist if there is difficulty in seeing.
The angle between incident and reflected rays is $i+r=2i$. So $2i=90^\circ$ and $i=45^\circ$.
$45^\circ$.
Multiple reflections continue back and forth between parallel mirrors.
Infinitely many images.
After two reflections from perpendicular plane mirrors, the emergent ray becomes parallel to the incident ray but travels in the opposite direction.
He can see only those images for which reflected rays from the mirror can reach his eyes. Use straight-line reflection construction from each object image behind the mirror to decide P, Q and R.
The image is behind the mirror at the same perpendicular distance as A is in front. Any observer who receives reflected rays can see the same image. The image position of A does not move when the observer moves.