Galileo played with this formula until, by the late fall of ... and blurriness caused by the curvature of the "objective" lens—the convex lens at the far end of the telescope—Galileo ground ...

\(power \ of \ a \ lens \ (D) = \frac{1}{focal \ length \ (m)}\) A lens has a power of -3.33 dioptres. Calculate the focal length and state what type of lens it is.

Convex and concave lenses can both be used to correct defects of vision. The most commonly occurring defects of vision are ‘short sightedness’ and ‘long sightedness’. People who are ...