Question

Problem 6) [Svelto, 1.7] Objective: Perform a rough estimate and comparison of laser properties (brightness in this case) to conventional light sources. The brightness of probably the brightest lamp so far available (PEK Labs type 107/109, excited by 100W of electrical power) is about 95 W/cm- sr in its most intense green line a 546 nm) Compare this brightness with that of a 1 W Argon laser 514.5 nm),which can be assumed to ntoe assumed to be diffraction limited.

Answer 1

Expression for Brightness of a diffraction - limited beam is, B = [2/beta pi lambda]^2 P Here, p is the power, lambda is the wavelength, beta numerical coefficient of order unit (almostequalto 1). Using the equation calculate brightness of 1W argon laser. B = [2/(1) pi(514.5 times 10^-9 m)]^2 (1.0 W) = 1.53 times 10^12 W/m^2 Now compare brightness of laser with lamp brightness, B_laser/B_lamp = 1.53 times 10^12 W/m^2/95 times 10^4 W/m^2 = 1.6 times 10^6 B_laser almostequalto 1.6 times 10^6 B_lamp