Unwrapping the magic of microwave oven

How does a microwave oven function?

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A microwave oven uses microwaves, a type of electromagnetic radiation, to cook or heat food. These microwaves are generated by a device called a magnetron.

• The microwaves penetrate food and cause water molecules, fats, and sugars in the food to vibrate rapidly.
• This vibration produces heat due to molecular friction, which cooks the food from the inside out.
• The frequency of microwaves used is usually 2.45 GHz, ideal for exciting water molecules.

Why can’t we use metal utensils in a microwave?

Microwaves reflect off metal surfaces instead of passing through them.

This reflection can:

• Cause sparking or arcing (small electric discharges)
• Potentially damage the magnetron
• Even start a fire in extreme cases

Metals also do not absorb microwaves, so they don’t heat up the food inside them effectively.

Why microwave-safe utensils don't heat up but food does?

Microwave-safe utensils are made of non-conductive materials like ceramic, glass, or specific plastics. These materials:

• Do not contain water molecules, so they do not absorb microwaves and thus do not heat up (or do so very slowly).
• Allow microwaves to pass through and reach the food, which then gets heated by its own water content.

However, such utensils can become hot indirectly through conduction from hot food.

Important points box (Civil Services-oriented notes)

Sample questions for civil services exam

Short answer type questions:

1. What is the principle behind microwave cooking?
2. Why is it unsafe to use metallic containers in microwave ovens?
3. What type of utensils are microwave-safe and why?

Long answer type question:

Q: Explain the working principle of a microwave oven. Why are certain utensils considered unsafe for microwave use? Also, discuss the material properties of microwave-safe utensils.

Answer hints:

• Begin with magnetron and microwave radiation
• Explain heating via molecular vibration
• Describe behaviour of metals vs. non-conductive materials
• Conclude with practical safety and design considerations

Analytical /applied question (GS Paper 3 - Technology & Safety):

Q: Microwave ovens represent a breakthrough in household cooking technology. However, they also pose specific safety concerns. Critically examine the science behind microwave heating and assess the safety implications of material choice in daily usage. Suggest awareness measures to reduce microwave-related accidents.

Answer hints:

• Start with brief intro of microwave technology
• Explain working principle
• Assess safety concerns (metal, overheating, plastic leaching)
• Suggest public awareness, labeling standards, safety guidelines
• Link with topics under Science & Tech, Disaster Safety in household, and Consumer Awareness