Question

Q. state the factors on which focal length of a lens depends

Q. If lens A has a bending angle of 22° and lens B has a bending angle of 47° then which has more converging capability? which one has shorter focal length?

Q. magnification of convex mirror is always less than 1...explain why??​

Answer 1

Explanation:

Focal length depends on colour of light because changing color changes wavelength which in turn changes the convergence point, so focus position changes and hence focal length also changes. It also depends on curvature of lens,

i.e.

f

1

=(

M

1

M

2

−1)(

R

1

1

−

R

2

1

)

where R

1

,R

2

are radius of curvature of two sides of lens. And M

2

is refractive index of material of which lens is made of and M

1

is refractive index of surrounding medium. And by this formula we see that focal length is also dependent on the material of lens.