11
Khyati
·2010-10-12 10:50:49
5) There is a dust particle on a glass slab of thickness t and refractive index 1.5. When seen from one side of the slab, the dust particle appears at a distance 6cm. From other side it appears at 4cm. find the thickness t of the glass slab
39
Dr.House
·2010-10-12 12:58:27
5th one done here:
http://www.goiit.com/posts/list/optics-dust-particle-on-a-glass-slab-1001157.htm
39
Dr.House
·2010-10-12 13:01:36
1)
keeping the mirror constant
implies that particle is moving at vel of 14 towards the mirror
and man is moving at 2 towards the mirror
therefore vel of particle wrt man is 14-2=12 which will be the velocity of the image too
hope someone verifies it
39
Dr.House
·2010-10-12 13:03:55
4)
again its relative velocity
keep the mirror constant
vel of object wrt mirror is 3i+4j+5k-(4i+5j+8k) =-1i-1j-3k
vel of image will be opposite to this
so vel of image will be i+j+3k
am not so sure , but hope someone verifies it
11
Khyati
·2010-10-12 16:24:20
Answers given in the book ( DC Pandey)
1) 26cm/s
2)4.8i+ 1.4j
3)0.5m
4)3i + 4j + 11k
5)15cm
11
Khyati
·2010-10-12 16:29:10
@ SHANKS SIR
For the 4th one I got the same answer as yours, but its wrong
1st answer wrong according to th book, but I think its correct because am getting the same answer (and its making sense too)
thanks for and the link and help [1]
106
Asish Mahapatra
·2010-10-12 21:09:30
DCP has given correct ans for Q1.
see fig for all explanation

106
Asish Mahapatra
·2010-10-12 21:15:07
4) A plane mirror is moving with velocity 4i + 5j + 8k. A point object in front of the mirror moves with velocity 3i + 4j + 5k Here k is along the normal to the plane mirror and facing towards the object. he velocity of the image is?
see velocity of image wrt observer will change only in the direction of the normal from the plane of mirror to the object.
i.e. here only the k component will change . other component will remain same as they have no relation with the mirror's velocity.
So, the vel of image wrt observer (i.e. point object)
= 3i + 4j + (5 + (8-5))k
= 3i+4j+11k
106
Asish Mahapatra
·2010-10-12 21:17:22
2) similarly find component of motion which is perpendicular to plane of mirror and joins the particle. the relative velocity will be affected only in this direction (similar to Q4.)
if you want derivation for this, try assuming a coordinate system as I have done in solving Q1. but now take two dimensional coordinate systems.
11
Khyati
·2010-10-13 00:40:37
Thanks a lot Asish for the awesome explanation. [1]