The amount of light produced by a cylindrical fluorescent light bulb depends on its lateral area. A certain cylindrical fluorescent light bulb is 36 inches long, has a 1 inch diameter, and is manufactured to produce 0.283 wants of light per square inch. What is the best estimate for the total amount of light that it is able to produce?

The Hale telescope of Mount Palomar has a diameter of 200 inch. What is its limiting angle of resolution for 600 nm light ?

The hale telescope of mount Polamor has a diameter of 200 inches. What is its limiting angle of resolution for 600 nm light?

A window is in the form of a rectangle, together with a semi-circle on its top side as diameter. If the perimeter of the window is 80 inches, determine the dimensions of the rectangle, so that a maximum amount of light may be admitted.

Which of the following is correct? (i) A fluorescent lamp, like the ones commonly found in offices, is a discharged tube in which the inner surface is coated with a fluoresecnet material such as zinc sulphide which is also used on TV screen. (ii)The fluorescent tube is filled with ercury vapor at low pressure. Excitation of the Hg atoms by electron bombardment cause the emission of light in the green, blue, and ultraviolet (UV) regions. (iii) When the light strike the inner glass wall, most of the UV light is abosorbed by the fluorescent material, which then emits a multitude of longer wavelengths that combine to produce white light. (iv) Fluorescent lamps are more enegry-efficient and, hence, cheaper to operate than tungsten lamp (ordinary light bulbs).

Photometry: The measurement of light as perceived by human eye is called photometry. Photometry is measurement of a physiological phenomenon, being the stimulus of light as received by the human eye, transmitted by the optic nerves and analysed by the brain. The main physical quantities in photometry are (i) the luminous intensity of the source, (ii) the luminous flux or flow of light from the source and (iii) illuminance of the surface. The SI unit of luminous intensity (I) is candela (cd). The candela is the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540 xx 10^12 Hz and that has a radiant intensity in that direction of 1/683 watt per steradian. If a light source emits one candela of luminous intensity into a solid angle of one steradian, the total luminous flux emitted solid angle is one lumen (1m). A standa o incandescent light bulb emits approximately 1700 lumens. What is photometry?

A light rod of length 2 m is suspended from the ceiling horizontally by means of two vertical wires of equal length tied to its ends. One of the wires is made of steel and is of cross section 0.1 cm^(2) . The other wire is a brass of cross section 0.2 cm^(2) . A weight is suspended from a certain point of the rod such that equal stress are produced in both the wires. Which of the following are correct?