# 14 - Optics Questions Answers

Joshi sir comment

A boy is walking under an inclined mirror at a constant

velocity V m/s along the x-axis as shown in figure. If the

mirror is inclined at an angle θ with the horizontal then

what is the velocity of the image?

Joshi sir comment
Physics >> Optics >> Refraction IIT JEE
Joshi sir comment

Can You Please Explain the Cartesian method for mirror and Lens?

Joshi sir comment

Cartesian method is the method of sign convention

Sign Convention for Spherical Mirrors and Thin Lenses

Spherical Mirrors                   Lenses
Focal Length            - for concave mirrors            + for a converging lens
+ for convex mirrors               - for a diverging lens
Object Distance           - real object                     - real object
+ virtual object                 + virtual object

Image Distance           - real image                          + real image
+ virtual image                   - virtual image
Magnification            + for erect image                 + for erect image
- for inverted image            - for inverted image

when two plane mirror inclined to each other at an angle 60degree , the number of image =?

please explain with ray diagram .

Joshi sir comment

angle is 60

if object is placed symmetrical then images = 360/60 - 1 = 5

if unsymmetrical then 360/60 = 6

what is defination of polarization

Joshi sir comment

Polarisation is the phenomenon to turn light in a particular direction by any means

for an aperture of size a illuminated by a parallel beam of light having wavelength λ the fresnel distance is

ans a^2/λ       what is fresnel dist.??

Joshi sir comment

fringe width β = λD/d

for β = d , D is called fresnel distance

so d2 = λD

so D = d2/ λ

now change d by a

which physical quantity has its unit as LUX??

Joshi sir comment

its illuminance

Physics >> Optics >> Refraction Medical Exam

if ω1 &ω2 are dispersive powers of lenses of focal length f1 & f2 respectively . then the condition of chromatic aberration for two lenses in contact is

1) ω1/ω2 = f2/f1

2) ω1/ω2 = f1/f2

3) ω1/ω2= - f1/f2

4) ω2/ω1= f1/f2

Joshi sir comment

3 is the true condition and can be proved

Physics >> Optics >> Photometry Medical Exam

IN D QUES OF RED ROSE IN WHICH  WE HAVE TO FIND COLOR WHY THE COMPLEMENT COLOR OF BLUE i.e ORANGE &RED WILL B SEEN