Microwave Lab Quiz

In this brief Lab Quiz, we analyzed the standing electromagnetic waves generated in a microwave oven. 
The Setup:

An arrangement of marshmellows are placed in a microwave

A burned area in the marshmellow arrangement is visible

The distance between noticible burn marks in the marshmellow
arrangment is measured - This is the distance between wave crests

A mug containing water is heated up by the microwave oven

• An arrangement of marshmellows are placed in the microwave such that the base area of the oven is covered
• The microwave is turned on long enough so that areas on the marshmellow arrangement have noticble burns
• The dimensions of the microwave are measured
• A mug containing water is heated up in the microwave

Measurements and Calculations:

• The dimensions of the microwave oven were measured as 23cm x 36 cm x 23 cm (L, W, H)
• The waves produced by the microwave are electromagnetic with a speed of propagation to be the speed of light, c; 3E8 m/s
• The burn marks on the marshmellow arrangement were measured to be 12 cm apart; This is the wavelength of the electromagnetic waves produced
• Using the relation between wave speed, frequency and wavelength, (v=wavelength*frequency), solving for frequency yields 1.25 GHz
• The water in the mug was heated for 30 seconds yielding a temperature increase of 37 degrees Celsius
• Relating the specific heat of water, it's mass (100 g), and change in temperature, the energy absorbed was calculated as 15,500 J
• Relating the energy absorbed by the water and the duration of time exposed to the microwaves, the power of the microwave was calcuated to be 515 W (J/s)

Calculations performed on quiz sheet