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Principles of Physics in Chemistry

Meera Madhu asked:
“is there any priciples of phy involed in chemical reactions ?”
Physics and Chemistry are the two main branches of Physical Science, the branch of science which discusses nature and its properties and the various phenomena associated with it.
Some of the Principles to mention are
The Principles of conservation,
Thermal expansion
How to hold a test tube, pipette, Burette etc?
(Visitors are requested to add more)

Why a sound is produced when a fluorescent tube breaks?

Why does a big  sound come when tube-light breaks?

(Question was posted by Vishwesh)

Answer: Every sound is produced by some vibrating bodies. In this case it is air surrounding the tube which vibrates.

Broken Tube LightInside the tube-light there is partial vacuum. When it breaks, the air surrounding the tube suddenly rushes into the vacuum and starts vibrating and thus produces the sound.

Questions from Relativity

Sam asks

  1. “After the Sun, the nearest star visible to the naked eye is Rigel Centaurus, which is 4.35 light years away. If a Spacecraft was sent there from earth at a speed of 0.80c, how many years would it take to reach that star from earth as measured by observers (a) On Earth; (b) On the Spacecraft? (c) What is the distance travelled according to observers on the spacecraft?”
  2. A beam of a certain type of elementary particle travels at a speed of 2.58 x10^8 m/s. At this speed, the average lifetime is measured to be 2.50 x 10^-8 s. What is the particles lifetime at rest?
  3. Imagine a rocketship takes off for a distant planet and can travel at many times the speed of light. (We know that this is impossible but let’s just say you can for this question). Observers on the planet are viewing the incoming spaceship through a powerful telescope. Describe what they will see from the moment the rocketship leaves Earth until it land on the observer’s planet. Support your answer with example equations.
  4. If you were on a rocketship travelling at 0.6c away from the sun, at what speed would the sunlight pass you?
  5. A 100 MeV electron, travelling at 0.999987c, moves along the axis of an evacuated tube that has a length of 3.00m as measured by a laboratory observer S with respect to whom the tube is at rest. An Observer S0 moving with the electron, however, would see this tube moving past her. What length would the tube appear to the Observer?

Why does a test tube seem silvery when put in water?

Amritha Asked:

Why does a test tube seem silvery when put in water?

This is due to Total Internal Reflection. When an empty test tube is inserted in water, the light trying to enter the test tube undergoes total internal reflection and shines like silver.

The air bubbles trapped in a glass paper weight a;lso shines like silver due to TIR.

Fluorescent lamp flickers and incandescent lamp does not!

Swathi asked:

Why do fluorescent lights flicker (tube lights) while Incandescent bulbs don’t , especially when they are switched on..Is it an effect of the pulses as sensed by the retina?


If your question is regarding the start up flickering,

the fluorescent lamp requires a very high voltage to start conducting. In a lit up tube light, the conduction is taking place through the gas filled inside the tube. As you know, air is a bad conductor. To make it conducting, it is to be ionized first. This is done by developing a very high potential difference between the two ends of the tube by the combined action of starter and the choke. Starter is a make and break arrangement which makes the supply intermittent. When the supply is disturbed, a huge potential difference is developed and flashes produced inside the tube ionizes the gas inside the tube. After such a few occurrences, the gas will be ionized enough to make the gas conducting. During this process lot of UV radiations are emitted. This strikes the fluorescent coating on the tube which converts UV radiations to visible light. So, the tube light flickers due to the action of starter during the startup time.

But, if your question is with regard to the flickering of a lit up fluorescent lamp, …………. 

I will answer it later

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