12 - Optics Questions Answers

Physics >> Optics >> Refraction IIT JEE
Asked By: BHASKAR JHA
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Joshi sir comment

Let α is small angular displacement As shown x = lsinα and y = lcosα/μ now use sin2α+cos2α = 1

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

Asked By: BONEY HAVELIWALA
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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 .

Asked By: ASHOK SOLANKI
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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

 

Asked By: SAIFALI SALIM JAMADAR
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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.??

Asked By: SARIKA SHARMA
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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??

Asked By: SARIKA SHARMA
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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

Asked By: HIMANSHU
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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

Asked By: SARIKA
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Joshi sir comment

since only blue light is present so any other colour can not be the answer

Physics >> Optics >> Photometry Medical Exam

A RED ROSE IS KEPT IN BLUE LIGHT. WHAT COLOUR OF ROSE WILL BE SEEN?

Asked By: SARIKA
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Joshi sir comment

Since it is red rose it means it will absorb all colours other than red so in blue light it will be seen as black.

A transparent sheet of paper of refractive index 'n' and thickness 't' is pasted on one of the slits in YDSE  which uses monochromatic light of wavelength  'x'  . How many fringes will cross through the centre if the paper is removed ?

Asked By: NITIN RAO
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Joshi sir comment

total path difference created by the paper = (n-1)t

geometrical path difference = yd/D

so position of central maxima will be obtained by eq. (n-1)t  = yd/D

here y is position of central bright, d is slit appeture and D is distance between slits and screen.

so y = (n-1)tD/d

width of maxima = xD/d ,                 x is wavelength of light

so no. of fringes shifted = [(n-1)tD/d]/[xD/d] = (n-1)t/x

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