Hi guys.

Can you guess the title of my next video Hurry up.

Write your guess in the comments section below.

How to stop a sneeze?

By saying Cheese.

Dude.

At least once think of a sensible answer.

A sneeze is controlled by the trigeminal nerve present in our face.

When irritants like dust and pollen enter our nose.

The trigeminal nerve triggers sneezing to expel them out with huge force and pressure.

Now, many people close their nostrils and mouth to stop a sneeze.

But this can lead to transfer of force and pressure inside their heads.

Thus damaging their eardrums or other tissues.

Normally, sneeze should not be stopped.

But in exceptional situations.

A relatively safe way to stop a sneeze is to press our finger above our upper lip.

Since the trigeminal nerve is also present above our upper lip.

Such pressing action also sends a signal through that nerve to the brain.

This interrupts the sneeze response and distracts the brain, thus helping in stopping our sneeze.

How do glasses work?

They work very hard to make us look intelligent and studious.

No.

When light from an object reaches our eyes, the cornea and lens refract the light.

In a person having perfect vision, the refracted light is accurately focused on the retina.

The retina then sends information to the brain, informing it about the object.

However, in some people, the light does not get properly focused on the retina, causing blurry vision.

When light gets focused before the retina, the defect is called myopia.

Myopia can be corrected using glasses having concave lenses.

Whereas, when light gets focused behind the retina, the defect is called Hyperopia or hypermetropia.

Hypermetropia can be corrected using glasses having convex lenses.

Apart from these, there are other defects also like presbyopia and astigmatism.

Which can also be corrected using glasses having appropriate lenses.

How do geckos stick to walls?

Using a two-sided tape.

No.

The toes of geckos have hair like structures called setae.

Each of these setae branches into tiny bristles called spatulae.

Spatulae help geckos to stick to many surfaces using the principle, 'Opposite Charges Attract'.

Now, molecules of a body or an object are usually electrically neutral.

But these molecules have a side that is more positive and a side that is more negative.

When geckos walk on walls.

They place their spatulae at such an angle that their positively or negatively charged sides.

Get attracted to the opposite charges present on the wall's surface.

These forces of attraction are called Van Der Waals forces.

That's an impressive name.

Now, a gecko has billions of spatulae on its feet.

Hence, they create enough Van Der Waals forces so that geckos can stick to walls.

Topic: Resonance.

How does sound break glass?

Obviously, using a hammer.

No.

It is because of resonance.

I know.

Resonance means to keep calm and balance.

No.

Wait, I'll explain.

Every object when struck vibrates at its natural frequency.

If we make sound having a frequency which matches the object's natural frequency.

Then that object starts to vibrate.

This phenomenon is called resonance.

So, this was the reason why my legs started to move when the music system was switched on.

Just listen.

Every glass is made up of different materials.

However, all of them have a natural resonant frequency.

Hence, when we make sounds which match their resonant frequencies, the glasses start to vibrate.

As glass is a brittle material, louder the sound.

More violently will it vibrate causing the glass to shatter into pieces.

Topic: Sound.

Why do we hear echoes?

Hey.

Hold On.

Don't go into that room.

You don't want to listen to me.

Okay.

Then go ahead.

See, I warned you.

Will you listen to me now?

Don't worry.

The sound you heard was just an echo of your voice.

Let me explain what an echo is.

When we speak or laugh in a big empty hall, we hear our own sound repeatedly.

This is because our sound waves get reflected from the walls of the hall back to us.

The reflected sound that we hear is called an echo.

Hence, an echo is defined as the repetition of sound caused by the reflection of sound waves.

From a hard surface back to the listener.

Hey.

What are you doing?

Are you trying to hear an echo?

It is not that easy.

There are 2 ideal conditions for an echo to be heard.

When we speak or laugh, we hear our original sound at that moment.

The sensation of this original sound remains in our brain till 0.1 seconds.

This time is called the persistence of hearing.

When we utter sounds, some of our sound waves get reflected while some get absorbed.

If the reflected sound waves reach our ears before the completion of 0.1 seconds.

Then our brain does not perceive the original and reflected sounds as separate sounds.

They are interpreted as one sound.

Therefore, in order to hear two distinct sounds or an echo.

The time gap between the original sound.

The reflected sound or echo Should be at least 0.1 seconds.

This is the first condition for an echo to be heard.

Do you know when the time gap will be more than 0.1 seconds?

This gets us to the second condition for an echo.

The minimum distance between the speaker and the reflecting surface should be at least 17.2 meters.

When the distance is 17.2 meters and we start speaking.

Assume that the original sound reaches our ears at this time.

The reflected sound reaches our ears at this time.

Then the time interval between the reflected sound and the original sound will be equal to 0.1 seconds.

As a result, we will be able to hear an echo.

Alright.

Now, let us try and hear an echo in this room?

It is even bigger than the previous room.

Now, why can't we hear an echo?

This is because there are many soft furnishings like sofas, carpets, curtains, etc., in this room.

They absorb most of the sound waves.

As the sound waves do not get reflected, we are not able to hear an echo in this room.

Hence, one more thing to consider.

If we want to hear an echo, is that there should be minimal use of such sound absorbing materials.