What will happen to the focal length if the convex lens is dip inside the water.
Focal length of a lens depends on the refractive index of the material of the lens relative to its surrounding medium ....
Hence .. when the lens is placed in water instead of air .. the focal length increases ..... bcoz the R.I of water is more than R.I of air .....
Hope this helps !!!
Really speaking! Lenses depends on a specific property of refraction, which depends on the ratio of refractive indexes of the two media on either side of an interface.
Coming to Focal length of the lens ; the Focal length is inversely proportional to the Refractive index(bending of light) in the medium;
The refractive index ratio of glass(lens) to air is greater than the the refractive index ratio of glass(lens) to water i.e 1.33/1(=1.33) >1.33/1.44 (=0.9236)
So,the focal length increases when it is dipped inside water