Question

A man was engaged as typist for the month of February in 2009. He was paid rs 500 per day, but rs 100 per day were deducted for the days he remained absent. He received rs 9100 as salary for the month. For how many days did he work?

Clue: non leap years has 28 days

Answer 1

9 1.Suppose you are in a dark room. Can A

you see objects in the room? Can you see

objects outside the room? Explain.

Ans. We see objects only when light reflected

by them enters our eyes. Since no light is

reflected from the objects in a dark room. we

are not able to see them. However. outside

the room. where light is available. objects Irregular

surface

can relect light and thus. we are able to Fig. 16.1: Diffused Reflection]

see them. A. B. C. D are the parallel rays. Their

reflected rays follow the laws of reflecion.

Reflected rays are not parallel because the

9.2. Differentiate between regular and

diffused reflection. Does diffused reflection

mean the failure of the laws of reflection ? surface is irregular.

Ans.

9.3. Mention against each of the following Regular Reflection Diffused Reflection

whether regular or diffused reflection will

1.It takes place when 1.It takes place when

take place when a beam of light strikes.

light reflects from a light reflects from

Justify your answer in each case.

plane. smooth and rough surface.

(1) Polished wooden table (2 Chalk

powder (3) Cardboard surface (4) Marble

shiny surface.

2. If incident rays are 2. If incident rays are

floor with water spread over it (5) Mirror

(6) Piece of paper parallel. all the rays parallel. the rays

are parallel after are not parallel

Ans. (1 )A regular reflection takes place on

a polished wooden table because its suriace reflection. after refection.

3. Reflection from the 3. Reflection from the is smooth and polished.

plane mirror is a paper or wood is an ( 2)A diffused reflection takes place on a

chalk powder because its surface is uneve

Tegular rellecion. irregular reilection.

(3) Cardboard surface has minute irre

gularities on it. so it will have a diffustu

Diffused reflection is not due to the failure

of the laws of reflection. It is caused by the

reflection.

iTregularities in the reflecting surface.

4) Marble floor with water spread over

will have regular reflection. It will acts 1

a plane mirror.