1A luminous object is seperated from a screen by a distance D.What is the greatest focal lenth a lens could hace to foucs the object on screen??
A small object is placed 10cm in front of a plane mirror. If u stand behind the object 30 cm from the mirror, and look at its image, then for wat distance must you focus ur eyes??
My ans : 40cm
Is dat wrong??-It is just a verification, coz it is given wrong...
-
UP 0 DOWN 0 0 4
4 Answers
111See its a mirror therefore
distance of the object from a mirror will be equal to the distance of the image from the mirror inside in the mirror
Therefore since the object is 10cm from the mirror . The image will be 10cm inside
You are standing 30cm from the mirror
Image is 10cm inside
The distance is therefore 40cm the answer is rite
11#2
x be the distance between the lens and object
1/D-x + 1/ x = 1/f
1/f = x + D -x/x(D-x)
f = (xD -x 2)/D
df/dx = (D -2x)/D
0 = (D -2x)/D
0 = 1 - 2x/D
2x/d = 1
x = d/2
f =( D2/2 -D2/4)/D
F = D/2 - D/4
F = 2D - D/4
F = D/4
1@virang tnx....den i hav 2 change my reference buk... gud no of questions but.. lots of errors....:(