28. A photon of electromagnetic radiation contains 7.5 x 10-20 joules of energy. What is the frequency of this photon?

a) 8.8 x 10-15 Hz b) 4.4 x 10-13 Hz c) 5.1 x 10-3 Hz d) 6.63 x 1010 Hz e) 1.1 x 1014 Hz

29. Blue light has a wavelength of 6.0 x 10-7 meters. What is the energy of a photon of this light?

a) 2.1 x 1023 joules b) 3.3 x 1020 joules c) 5.0 x 1014 joules d) 3.3 x 10-19 joules e) The energy cannot be determined from the information given.

30. What is the wavelength of microwave radiation that contains 1.5 x 10-23 joules of energy per photon?

a) 1.33 x 10-3 meters b) 4.5 x 10-3 meters c) 9.9 x 10-3 meters d) 1.33 x 10-2 meters e) 4.5 x 10-2 meters 38. A tankless hot water heater saves energy by heating water only when it is needed. One model of tankless hot water heater costs $850 to purchase and $65 per year to operate. A conventional tank hot water heater costs $650 to purchase and $115 per year to operate. What is the payback time for this tankless hot water heater?

a) 4.0 years b) 4.5 years c) 5.0 years d) 6.5 years e) more than 10 years

39. A glass window measures 1.5 meters by 2.0 meters in size. The glass is 2 cm thick. How much heat flows through this window when the outside temperature s 10 C and the inside temperature is 23 C? The thermal conductivity of glass is 0.84 J/s m C.

a) 16.4 J/s b) 35.3 J/s c) 475 J/s d) 1,638 J/s e) 1,833 J/s

40. Energy flows at a rate of 80 BTU's per hour through a 3 ft by 6 ft insulated door. The temperature on the outside of the door is 30 F and the temperature on the inside is 70 F. What is the R-value of the insulated door?

a) 0.1 ft2 F/(BTU/hr) b) 3.0 ft2 F/(BTU/hr) c) 6.5 ft2 F/(BTU/hr) d) 9.0 ft2 F/(BTU/hr) e) 18 ft2 F/(BTU/hr)

41. A sound wave travels with a speed of 300 m/s. If its wavelength is 40 meters, what is its frequency?

a) 0.13 Hz b) 0.15 Hz c) 6,5 Hz d) 7.5 Hz e) 300 Hz

45. How much thermal energy is required to change the temperature of a 1 kg object by 25 oC if the object has a specific heat of 0.9 calories/kg oC?

a) 27.8 calories b) 25.9 calories c) 22.5 calories d) 20.25 calories e) 0.036 calories

46. A hairdryer on its "high" setting uses 800 Watts of electric power. If this hairdryer is plugged into a typical U.S. power outlet (120 V) what is the current supplied by the outlet?

a) 0.15 amperes b) 6.7 amperes c) 9.6 amperes d) 18 amperes e) 44 amperes