Question

Microwave ovens use microwave radiation to heat food. The microwaves are absorbed by moisture in the food, which is transferred to other components of the food. As the water becomes hotter, so does the food. Suppose that the microwave radiation has a wavelength of 11.2 cm. How many photons are required to heat 200 mL of coffee from 25 C to 63 C?

Answer 1

As q = MCAT where m = mass of substance c = heat capacity of coffee AT = change in temperature ДТ= Т – Т Ti = 25° c = 25+ & 73= 298k Ty = -63° C = 63 + 73 = 336 K. AT= 336 - 298 AT= 38K e We take e = 4.181 I gtkt heat capacity of water = 7 e = 1 gult (420) I heat capacity of coffee / As density, p = mars volume mass = acoml x I guilt mass = 200 g CS Scanned with game onnea o g x 4.181 Igt ktx 38 K

Q- 31-7756 KJ GK 5 = 103 J) E = hu = he where h = Planck} constant 1. c = speed of light cs Scanned with de Wavelength CamScanner

-_-Energy, E = 6.6 X 1624 Js X 3x10 mest - 112cue - Energy of photon, 62 1:3678.x. 10-24 J_(lamz 10-2 m) vo. of khatons required = 31.77.56 x 103 I _ )-7_678 x 1624 J. - =1.79_x 1028 = No. of phatons required to heat daoul of coffee from groc to 63 c = 1179 x 1,28 Scanned with GamScanner