Guest Lecture

The IIS University

Department of Physics

Report: Guest Lecture

Date: 31^stAugust,2017

Time: 10:00 am

Guest speaker: Prof. Deepak Bhatnagar, Head, Dept. of Physics, University of Rajasthan, Jaipur

 Firstly he introduced everyone to the word “Microwaves” that its frequency ranges from 1 GHz to 300GHz. The main characteristics of microwaves originate from the small size of wavelengths in relation to the sizes of components or devices commonly used. The main advantages of microwaves is the low attenuation and low power requirement.

He then explained the working of Microwave Oven.  The microwave energy gets reflected from metal walls thus reaches to the food from all directions and microwave energy is absorbed by food and water. Basically the heat is produced due to the vibrational motion of water molecules. This is why when we heat suji in oven it does not burn after a particular period of time because when all moisture present in it is vanished there is no source of heating left.

Taking the example of his wife, he described how some people think that cooking in microwave oven has hazardous effects as it produces chemical reactions in the body and cause cancer, tumour and other diseases. To which he politely underlined the fact that in any chemical reaction bonds are made and broken. Certain amount of energy is required to break bonds. And photons don’t have enough energy to break the bonds. It has energy of 10^-5eV, which is too less to break any kind of bond. Like, hydrogen bond, covalent bond, ionic bond or any other bond.

In fact, in Green Chemistry microwaves are used to increase the rate of reactions, the work which takes time of a day gets completed in minutes. It does not have energy to create polar or bipolar products which cause cancer, it just increases the rate of reaction. Hence proving it is completely safe to use microwave ovens. He just warned us that after cooking in microwave oven wait for five minutes and then open the slab, because the microwaves are obviously harmful for our skin.

There are certain areas of our skin which are highly sensitive to microwaves, that include portion near the ear, heart, kidney, eyes and male testicles because these are the areas where the blood flow rate is too less. It has been observed that people who work on the top of the tower suffer eye problems due to the microwaves as they heat up the water of eyes.

Second most usable device is the Mobile Phone. It has been proved that the ideal time to use mobile phones is 19 minutes per day. The Specific Absorption Rate (SAR) is 1.8GHz, not very far from 2.45GHz, which is the resonance frequency of water. When we use mobile phones the water around the ear is heated up and there is no space for air circulation, which obviously is very harmful. Even if we are not using mobile phone, we should keep it at a certain distance because it is continuously radiating energy as it is connected to the nearest tower.

The common complaints due to microwaves are sleep disruption, depression, fatigue, headache, forgetful memory, dizziness, visual disorders, buzzing in head and altered reflexes. But no medical journal or research paper proves that microwaves cause diseases like cancer and tumour.

He then explained the pattern of a cell tower antenna, that the area of least microwaves are just below the tower and we can see birds making nests at the same spot. KapilSibbal suggested to reduce power to 10 times, the recommended international limit adopted by India is 9.2 w/m² and even if we reduce it to 0.92 w/m² it is still very high.

He concluded his presentation with safety precautions to be taken which are as follows:

• Limit use of cell phone
• Talk for short duration on mobile phone
• If possible use SMS
• Use cell phone with low SAR value
• Prefer using landline as it is just audio signal
• Use earphones or speakers

In the end we learnt about how microwaves are useful for us only if we use them wisely.