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## E+M Warmups

Physics is not a discipline, but a way of looking at the world. See if you can use your sense of the world to explain everyday phenomena.

# Level 1

What is causing the reversal of the colors in the glass?

We can image bacteria, snowflakes, and ants using the optical microscope, depending on the power of our lens. Why can't we use it to see atoms?

Ignore electron microscopes.

Suppose your friend lives in Sydney, Australia, and today the Indian Prime minister, Narendra Modi, is about to deliver a speech in the Opera House. Your friend has reserved a seat 20 meters from the microphone. You are listening to the same speech on the radio in Mumbai, roughly 10,000 km from Sydney.

Suppose the time it takes the sound to reach you is $$t_\textrm{radio}$$ and the time is takes to reach your friend is $$t_\textrm{live}$$. How much faster the sound reach you, compared to your friend (i.e. find $$t_\textrm{live}/t_\textrm{radio}$$)?

Details and Assumptions:

• Take the speed of sound to be $$300 \text{ m/s}$$.
• The speed of radio waves is $$300,000 \text{ km/s}$$.
###### Image Credit: Youtube Prime Minister Narendra Modi's Full Speech In Sydney, Australia.

An incandescent light bulb gets hot because

###### Image credit: Wikipedia Ulfbastel

As shown above, a charged particle $$A$$ with mass $$m$$ is placed between two parallel charged plates parallel to the ground with the negatively charged plate closer to the ground. The distance between the two plates is $$d$$ and the electric potential difference between the two plates is $$V$$. If the particle is stationary, then what is the magnitude of the quantity of the electric charge of $$A?$$

Note: $$g$$ denotes the gravitational acceleration.

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