You are given the following three lenses. Which two lenses will you use as eyepiece and as an objective to construct an astronomical telescope? Give reason .
`{:("Lenses","Power(D)","Aperture(cm)"),(L_1,3,8),(L_2,6,1),(L_3,10,1):}`

You are given the following three lenses. Which two lenses will you use as eyepiece and as an objective to construct a compound microscope ? . {:("Lenses","Power(D)","Aperture(cm)"),(L_1,3,8),(L_2,6,1),(L_3,10,1):}

Two lenses of focal lengths 6cm and 50 cm are used in construction of a telescope. Which lens will be used as an objective and why?

A fire engine raises 6 kL of water per minute to a height of 2m and ejects it at 9.2m*s^(-1) . Find the power of the engine. Given mass of 1L of water is 1 kg.

In a sonometer, two adjacent wires of the same material are stretched under the same tension. The first wire is thicker than the other. The corresponding frequencies of length l_(1) and l_(2) of the sonometer wires are in unison with a tuning fork. Which of the following is correct ? Give reasons. (i) l_(1) = l_(2) (ii) l_(1) lt l_(2) (iii) l_(1) gt l_(2)

If l_(1), m_(1), n_(1) and l_(2), m_(2), n_(2) are direction cosines of two mutually perpendicular straight lines, then prove that the direction cosines of the straight line which is perpendicular to both the given lines are pm (m_(1)n_(2)-m_(2)n_(1)), pm (n_(1)l_(2)-n_(2)l_(1)), pm (l_(1)m_(2)-l_(2)m_(1))