Geometrical Optics QA 5
Download as PPTX, PDF3 likes219 views
The document discusses a physics problem involving a concave mirror and a convex lens setup, focusing on the magnification produced by the system. It details the calculations for magnification in both air and a medium with a given refractive index, along with the necessary lens and mirror equations. Ultimately, it concludes with the required ratio of magnifications for the described arrangement.
![Physics Helpline
L K Satapathy Geometrical Optics 5
Correct option = (d)
1 1 1 2 1 8 7 1 ' 140
' ' ' 35 20 140 140
v cm
v f u
2
140 7
20
m
1 2 2 7 14M m m
14 7
2
[ ]M ns
M
A
Refraction by lens ( in medium) :
35 , 20
2
f cm u u cm
Magnification by lens in medium is
Magnification by combination in medium is given by
The required ratio is](https://image.slidesharecdn.com/7rayoptics5-160707053531/85/Geometrical-Optics-QA-5-6-320.jpg)
Geometrical Optics QA 5
- 1. Physics Helpline L K Satapathy Geometrical Optics 5 Magnification by Lens Mirror System JEE Question O
- 2. Physics Helpline L K Satapathy Geometrical Optics 5 Question : Consider a concave mirror and a convex lens ( = 1.5) , each of focal length 10 cm , separated by a distance of 50 cm in air ( = 1) as shown in the figure. ( ) 2 ( ) 3 ( ) 5 ( ) 7a b c d Concepts : O15 cm 50 cm An object is placed at a distance of 15 cm from the mirror. The erect image formed by the combination has a magnification M . When the arrangement is placed in a medium of refractive index 7/6 , the magnification becomes M. Then M/ M is Focal length of a lens of refractive index and radii of curvature R1 and R2 is given by 1 2 1 1 1( 1) f R R When the lens is placed in a transparent medium of refractive index , then 1 2 1 1 11 f R R Lens equation1 1 1 v u f Mirror equation 1 1 1 v u f
- 3. Physics Helpline L K Satapathy Geometrical Optics 5 Answer : 1 1 1 1 1 1 1 1 10 15 15 10 30v f u I1 30 cm 50 cm Reflection by mirror ( in air ) : 1 30 2 15 vm u 10 , 15f cm u cm Image I1 is formed 30 cm to the right of the mirror 30v cm Magnification by mirror is I1 becomes the object for the lens
- 4. Physics Helpline L K Satapathy Geometrical Optics 5 I1 I20 cm 20 cm Refraction by lens ( in air) : 1 1 1 1 1 1 1 1 10 20 10 20 20v f u 2 20 1 20 vm u 1 2 2M m m 10 , 20f cm u cm 20v cm Image I is formed 20 cm to the right of the lens Magnification by lens is Magnification by the combination in air is given by
- 5. Physics Helpline L K Satapathy Geometrical Optics 5 1 2 1 2 1 1 ' 7f R R In the medium ( = 7/6) : Reflection by mirror is not affected 1 1 2m m 1 2 1 2 1 1 1 1 1 11 2g f R R R R 3 6 9 21 2 7 7 7 g g m m Magnification by mirror is Calculation of focal length of lens in the medium : In air 1 2 1 1 11 ' g mf R R In medium ' 1 7 7 7 35' 10 2 2 4 4 2 f f cm f We have
- 6. Physics Helpline L K Satapathy Geometrical Optics 5 Correct option = (d) 1 1 1 2 1 8 7 1 ' 140 ' ' ' 35 20 140 140 v cm v f u 2 140 7 20 m 1 2 2 7 14M m m 14 7 2 [ ]M ns M A Refraction by lens ( in medium) : 35 , 20 2 f cm u u cm Magnification by lens in medium is Magnification by combination in medium is given by The required ratio is
- 7. Physics Helpline L K Satapathy For More details: www.physics-helpline.com Subscribe our channel: youtube.com/physics-helpline Follow us on Facebook and Twitter: facebook.com/physics-helpline twitter.com/physics-helpline