2. Methods

2.1 Equipment List


Figure 3: Equipment List


The equipment that we would be using are as follows:


  • Microwave oven (not pictured)
  • Plate (safe for use in microwave)
  • Plastic containers (safe for use in microwave)
  • Oven mitts
  • 3-6 eggs
  • Empty dry water bottle (to remove egg yolk)
  • Funnel
  • Squeeze bottle (to control amount of egg white)
  • Chocolate
  • Marshmallows (not pictured)
  • Ruler
  • Calculator





2.2 Diagrams of experimental setup
 


Figure 1: Experimental setup used to cook eggs in microwave oven partially




Figure 2: Experimental setup used to melt chocolate in microwave oven


2.3 Procedures


For egg white:


  1. Remove the microwave turntable.
    1. You may not be able to remove the drive mechanism for the turntable in your oven. In that case, you can make a support for your egg plate by placing a flat-bottomed, microwave-safe bowl upside down over the drive mechanism. Naturally, the bowl needs to be large enough so that the drive mechanism does not touch it. It also needs to provide sturdy support for the plate used for cooking the eggs.
  2. Crack an egg and separate out the egg white by allowing the white to drain into a bowl, and holding the yolk back in one half of the broken shell.
  3. Pour some of the egg white onto a microwave-safe plate.
    1. You should have puddles (or strips) of egg white that are at least 12 cm in diameter (in length).
  4. Put the plate in the oven, close the oven door, and cook the egg.
  5. Find the ideal cooking time of the egg for your microwave. 30 seconds should be a good starting point. If the egg is completely cooked, start over and decrease the time. If the egg is still totally uncooked, increase the time. If the plate moves, you'll need to start over with a fresh plate of uncooked egg white. The ideal result is to have egg white that is partially cooked in some places, and nearly completely cooked in other.
  6. Use oven mitts to remove the plate from the oven. Be careful not to move the egg on the plate. Allow the plate to cool.
  7. Measure the spacing between the cooked portions of the egg.
    1. The centers of the cooked portions will not be clearly defined.
    2. Your goal in making this measurement is to find:
      1. the average distance between the cooked portions, and
      2. an estimate for the error of your measurement.
    3. Measuring the "center-to-center" distance between adjacent cooked portions will give you the average spacing of the hot spots.
    4. Measuring the "edge-to-edge" distances (both shortest and longest) between adjacent cooked portions will give you upper and lower bounds on the error of your measurement.
  8. Clean and dry the plate, and repeat the experiment at least three times.
  9. Look at the label on the back of the microwave or the user manual to find the frequency of the microwave radiation the microwave produces. The spacing of the hot spots will be equal to half of the wavelength of the microwaves.
  10. Calculate the speed of the microwaves using the wavelength (measured) and frequency (from the oven label). Use the upper and lower boundary measurements to put error limits on your measurement.
  11. Find out if the results agree or are close to with the published values for the speed of light.
  12. Find out the error margin based on the actual speed of light.

For chocolate:


  1. Remove the microwave turntable.
    1. You may not be able to remove the drive mechanism for the turntable in your oven. In that case, you can make a support for your chocolate plate by placing a flat-bottomed, microwave-safe bowl upside down over the drive mechanism. Naturally, the bowl needs to be large enough so that the drive mechanism does not touch it. It also needs to provide sturdy support for the plate used for melting the chocolate.
  2. Put your chocolate in the middle of the plate.
  3. Heat the chocolate until it starts to melt in two or three places. This should take about 20 to 30 seconds.
  4. Take the chocolate out of the microwave - carefully! It will be hot. Measure the distance between the melted spots.
  5. Look at the label on the back of the microwave or the user manual to find the frequency of the microwave radiation the microwave produces. The spacing of the hot spots will be equal to one-half of the wavelength of the microwaves.
  6. Calculate the speed of the microwaves using the wavelength (measured) and frequency (from the oven label). Use the upper and lower boundary measurements to put error limits on your measurement.
  7. Find out if the results agree or are close to with the published values for the speed of light.
  8. Find out the error margin based on the actual speed of light.


For marshmallows:


  1. Remove the microwave turntable.
    1. You may not be able to remove the drive mechanism for the turntable in your oven. In that case, you can make a support for your marshmallow plate by placing a flat-bottomed, microwave-safe bowl upside down over the drive mechanism. Naturally, the bowl needs to be large enough so that the drive mechanism does not touch it. It also needs to provide sturdy support for the plate used for melting the marshmallow.
  2. Get your large, microwaveable dish and place a layer of marshmallows at the bottom of it.
  3. Cook the marshmallows on a low heat for a couple of minutes, or until you see parts of the marshmallows starting to bubble.
  4. Remove the dish and take a look at the marshmallows
  5. Look at the label on the back of the microwave or the user manual to find the frequency of the microwave radiation the microwave produces. The spacing of the hot spots will be equal to one-half of the wavelength of the microwaves.
  6. Calculate the speed of the microwaves using the wavelength (measured) and frequency (from the oven label). Use the upper and lower boundary measurements to put error limits on your measurement.
  7. Find out if the results agree or are close to with the published values for the speed of light.
  8. Find out the error margin based on the actual speed of light.


2.4 Risk Assessment and Management  


Risk
Assessment
Management
As the experiments involve heating, there is a risk of scalding the hand accidently.
Medium
Use gloves when heating or handling hot items. Do not heat pure liquids such as water. If unavoidable, stir vigorously before heating and leave container to stand before continuing stirring.
There is a risk of the incorrect use of equipment or cooking procedure.
Medium
Follow manufacturer’s recommended heating times for particular oven. Stir as required. Check if food is thoroughly cooked. Never put sealed containers or metal implements into a microwave. Foods containing alcohol should not be heated in a microwave oven. A fire extinguisher should be sited nearby.
There is a risk of obtaining a defective microwave.
Low
Routine checks should be made to identify damage to the inner walls and door seals, make sure the doors close properly and are not misaligned or warped, make sure hinges and door latches are not broken or loose and make sure the door closes properly and the oven switches off when it is opened.
There is a risk of spillage of food & liquids.
High
Ovens should be cleaned on a daily basis to prevent build up of spillages. Mop up and dry spills immediately both inside & outside oven. Routine checks should be made to identify damage to the inner walls and door seals.
Legend
Low
Unlikely and not severe harm

Medium
Likely but not severe OR Unlikely but severe

High
Likely and Severe harm

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