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Convergence lens with different radii

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A certain thin lens made from glass has surfaces with radii R1 = +10cm and R2= +8cm.
a) Sketch the lens?
b) Find the focal length?
c) Image distance for an object distance at 15cm?
 
Optics - Convergence lens with different radii, focal length and image distance Optics - Convergence lens with different radii, focal length and image distance - Physics Problems
A certain thin lens made from glass has surfaces with radii R1 = +10cm and R2= +8cm.
a) Sketch the lens?
b) Find the focal length?
c) Image distance for an object distance at 15cm?
 
A certain thin lens made from glass has surfaces with radii R1 = +10cm and R2= +8cm.
a) Sketch the lens?
b) Find the focal length?
c) Image distance for an object distance at 15cm?

Since both radii are positive, both surfaces are convex.
convergence lens with different radii

Using lensmaker’s equation
lensmaker’s equation

Using these values for radii and n = 1.5 for the index of refraction, we can find focal length for this lens
lensmaker’s equation
focal length
focal length
f = - 80 cm

To find image distance we apply thin lens equation
thin lens equation
thin lens equation
Image distance
Image distance
Image distance

s’ = 12.63 cm

This image is virtual, locate 12.63 cm in front of the lens. The effect of the lens is to diverge the incident rays, so that the object appears closer to the lens than it really is.
This image is virtual, locate in front of the lens
This image is virtual, locate in front of the lens
 
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