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Letusknowwhy

Apr 25, 2014



Letusknowwhy

Apr 25, 2014



May 24, 2014

#### what is first focus and second focus?What is the difference between them?



What is first focus and second focus? What is the difference between them?
Answer:  as a lens has two curved surfaces each curvature has a radius. So the lens has t...

May 26, 2014

#### how does the magnifying glass enlarge the image?what is its principle?Explain.



How does the magnifying glass enlarge the image? What is its principle? Explain.
Answer:  Magnifying glass enlarges or diminishes the image due to the refraction de...

Nandita Menon

Aug 10, 2014

#### convex lens are also used as spectacles or not?



yes  yo see the near things

Pawan Rout

Aug 21, 2015

#### WHAT IS INTERNAL REFLECTION?



when light goes from denser medium to rare medium and angle of refraction is greater than 90 then it does not refract it gets reflected back in same medium (then it obeys reflections law)
called internal...

Debraj

Feb 18, 2016

#### How to derive the gaussian's form of lens equation?



The derivation of the Gaussian form proceeds from triangle geometry. For a thin lens, the lens power P is the sum of the surface powers. For thicker lenses, Gullstrand's equation can ...

Siddhartha

Oct 9, 2017

#### 1) If half part of the lens is covered,the focal length does not change but the intensity decreases. Why? 2) A convex lens is placed in water. Its focal length will increase. Why? 3) The focal length of a thin convex lens is more than that of a thick convex lens. Why?



1.
To draw an image we just need two refracted rays. If you cover a half of lens then it won't receive light and therefore the light rays contributing in the image formation will be less and therefor...

Letusknowwhy

Apr 25, 2014



Letusknowwhy

Apr 25, 2014



May 24, 2014

#### what is first focus and second focus?What is the difference between them?



What is first focus and second focus? What is the difference between them?
Answer:  as a lens has two curved surfaces each curvature has a radius. So the lens has t...

May 26, 2014

#### how does the magnifying glass enlarge the image?what is its principle?Explain.



How does the magnifying glass enlarge the image? What is its principle? Explain.
Answer:  Magnifying glass enlarges or diminishes the image due to the refraction de...

Nandita Menon

Aug 10, 2014

#### convex lens are also used as spectacles or not?



yes  yo see the near things

Pawan Rout

Aug 21, 2015

#### WHAT IS INTERNAL REFLECTION?



when light goes from denser medium to rare medium and angle of refraction is greater than 90 then it does not refract it gets reflected back in same medium (then it obeys reflections law)
called internal...

Debraj

Feb 18, 2016

#### How to derive the gaussian's form of lens equation?



The derivation of the Gaussian form proceeds from triangle geometry. For a thin lens, the lens power P is the sum of the surface powers. For thicker lenses, Gullstrand's equation can ...

Siddhartha

Oct 9, 2017

#### 1) If half part of the lens is covered,the focal length does not change but the intensity decreases. Why? 2) A convex lens is placed in water. Its focal length will increase. Why? 3) The focal length of a thin convex lens is more than that of a thick convex lens. Why?



1.
To draw an image we just need two refracted rays. If you cover a half of lens then it won't receive light and therefore the light rays contributing in the image formation will be less and therefor...

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