Physics & Biology Hub

Physics & Biology Hub

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Planck's constant E = hf
6 or 4
Kepler's third law in the microcosm
hundred years, no one was able to understand and find

https://youtu.be/VEjP7BdZWLY
http://vixra.org/abs/1610.0103
http://search.rads-doi.org/index.php/article/435/4913

A platform where Physics and Biology students,teachers and lovers can share ideas,concepts,experiences as far as the subjects are matter of concern.

Physics and Biology Teacher is a platform intended for students pursuing physics and biology courses,It covers different subject matters on biology and physics both descriptive and numerical aspects of the material to help students to understand them. Students are advised to ask questions since that will be the means of understanding which part needs to be covered by the page.

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[05/03/20]   Hellow dear followers of our page we are sorry for being offline for quite some time now but we're now back. As #COVID_19 prevails and schools closed we understand there's a need for this online education platform. We appreciate your patience and promise to provide the help that you need as far as Physics and Biology goes.Thanks

29/01/2019
29/01/2019

[01/17/19]   THERMAL EXPANSION OF GASES

The Concept of Thermal Expansion of Gases
Gases expand when heated just like solids and liquids. This is because the average kinetic energy of the molecules in a gas is directly proportional to the absolute temperature of the gas. Heating the gas increases the kinetic energy of its molecules, making them vibrate more vigorously and occupy more space.
The Relationship between Volume and Temperature of Fixed Mass of Air at Constant Pressure
Investigate the relationship between volume and temperature of fixed mass of air at constant pressure
Three properties are important when studying the expansion of gases. These are; pressure, volume and temperature. Charles law states that the volume of a fixed mass of gas is directly proportional to the absolute (Kelvin) temperature provided the pressure remains constant. Mathematically V1T2 = V2T1.
Example 2
the volume of gas at the start is recorded as 30 cm3with a temperature of 30°C. The cylinder is heated further till the thermometer records 60°C. What is the volume of gas?
Solution:
We know, V/T = constant
Therefore,
V1/T1=V2/T2
V1 =30 cm3
T1 =30°C = 30+273 = 303K(remember to convert from Celsius to Kelvin)
T2 =60°C = 60+273 = 333K
V2 =?
V1/T1=V2/T2
V2=V1xT2/T1
V2=30x333/303
= 32.97 cm3
The Relationship between Pressure and Volume of a Fixed Mass of Air at Constant Temperature
Investigate the relationship between pressure and volume of a fixed mass of air at constant temperature
The relationship obtained when the temperature of a gas is held constant while the volume and pressure are varied is known as Boyle’s law. Mathematically, P1V1 = P2V2. Boyle's law states that the volume of a fixed mass of gas is inversely proportional to its pressure if the temperature is kept constant.
Pressure x Volume = constant
PxV = constant
Example 3
The volume of gas at the start is 50 cm3with a pressure of 1.2 x 105Pascals. The piston is pushed slowly into the syringe until the pressure on the gauge reads 2.0 x 105Pascals. What is the volume of gas?
Solution:
We know
p x V = constant
Therefore,
p1xV1= p2xV2
p1=1.2 x 105Pascals
V1=50 cm3
p2=2.0 x 105Pascals
V2=?
p1xV1= p2xV2
V2=p1xV1/p2
V2=1.2x105x50/2.0 x 105
V2= 30 cm3
The Relationship between Pressure and Temperature of a Fixed Mass of Air at Constant Volume
Investigate the relationship between pressure and temperature of a fixed mass of air at constant volume
To investigate the relationship between the pressure and the temperature of a fixed mass, the volume of the gas is kept constant. The pressure is then measured as the temperature is varied. P1/T1 = P2/T2 , this is called pressure law. The pressure law states that the pressure of a fixed mass of a gas is directly proportional to the absolute temperature if the volume is kept constant
Example 4
Pressure of gas is recorded as 1.0 x 105N/m2at a temperature of 0°C. The cylinder is heated further till the thermometer records 150°C. What is the pressure of the gas?
Solution:
We know, p/T = constant
Therefore,
P1/T1= p2/T2
p1=1.0 x 105N/m2
T1=0°C = 0+273 = 273K (remember to convert from Celsius to Kelvin)
T2=150°C = 150+273 = 423K
p2 =?
P1/T1= p2/T2
p2=p1xT2/T1
p2=1.0x105x423/273
= 1.54 x 105N/m2

The General Gas Equation from the Gas Laws
The three gas laws give the following equations:
1. pV = constant(when T is kept constant)
2. V/T = constant(when p is kept constant)
3. P/T= constant(when V is kept constant)
Which provide the general equation
PV/T=Constant

[01/17/19]   THE STRUCTURE OF HUMAN EYE

The eyeball is approximately spherical in shape. The wall of this sphere consists of two layers, the outer layer or sclera and the inner layer or choroid. The front portion of the SCLERA FORMS A TRANSPARENT CURVED section called the camera. The choroid layer is balance in order to prevent internal reflection and also to protect the light sensitive parts of the eye.
The aqueous and vitreous humour is jelly – like substance that fills the spaces within the eyeball. The aqueous humour is the salt solution of refractive index n, 1.38.Vitrous hurmour is a watery, Jelly substance of refractive index 1.34.Behind the cornea there is a colored diagram called the iris.
The iris has the central hole called the pupil. The iris contains muscles which control the size of the pupil. The size of the pupil decreased in the bright light and increased in the dim light.
Behind the pupil and there is a crystalline lens held in position by suspensory ligaments that are attached to the choroid layer. Near the suspensory ligaments are the ciliary muscles. The function of the suspensor ligaments there are the ciliary muscles.
The function of ciliary muscles is to control the thickness of the lens. The lens become thick when the ciliary muscles contract and thin when the ciliary muscles are relaxed.
At the back of the eye there is a retina (This is the part of the eye which is sensitive to light).Image formed is inverted formed on the Retina (This is the part of the eye which is sensitive to light.)
Image formed is inverted formed on the retina by successive refraction of light at the corner, the aqueous hurmour the crystalline lens and the Vitreous hurmour.Electrical signals are then transmitted to the Brain through the topic nerve. Finally, the brain interprets these signals.

ACCOMMODATION POWER OF THE HUMAN EYE

Accommodation is the process whereby the eye alters its focal length in order to form images of objects at different distances.
(Thickening or Thinning of the lens causes a change in its focal length).
The thickening or thinning of the crystalline lens is made possible by the action of the ciliary muscles. To view nearer object t, ciliary muscles contract, this makes the lens thicker.
In the relaxed state of ciliary muscles, the crystalline lens become thinner and enables the eye to see (view) distant objects. The farthest point which can be seen clearly is called the far point of the eye and the nearest point is called the near point of the eye.
The corresponding distance from these points to the eye are referred to as the maximum and least distance of district vision respectively. A normal eye (i.e. without defects of vision) has a far point at infinity and near point at a distance of 25cm from the eye. Structure of lens “view distant object”
The Defects of the Human Eye
Identify the defects of the human eye
Myopia or near-sightedness
• This defect causes person to see near object clearly while distant objects are not seen clearly.
• The strength of the cornea and the eye lens combination is too great even when muscles of the eye are completely relaxed.
• The focal length of the cornea and the eye – lens combination is always less than the distance to the retina.
• Images of distant object are formed in front of the retina even when eye is totally relaxed. However, an object that is closer can be brought into focus.
• In this situation the focal length of the cornea and the eye lens is so short that objects closer than the conventional (near point of 25cm) can be brought into focus. That’s why this condition is called Short sightedness (near sightedness).
• Since the problem is that the strength of the eye – lens and the cornea combination is too great, the solution is to provide eye glasses (or contract lenses) with negative lens.
• The negative lens weakens the strength of the cornea and eye – lens just enough so that the resulting focal length when the eye muscles are relaxed matches the distance back to the retina so that distant images are now in focused.
• The eye glass lenses are a negative lens that means they are thinner in the middle than at the edges.
• It is easy to identify this kind of eye glass lenses since acting by themselves they do not form a real image of an object at any distance.

Hypermetropia or far-sightedness
• This defect causes a person to see distant objects only and short-distance objects are not seen clearly.
• In the person with this condition, the strength of the cornea and the eye-lens combination is too weak when the eye muscles are totally relaxed. So the image of a distant object is formed behind the retina.
• The solution in the opposite of myopia. Victims should wear positive eye lenses which strengthen the corner and the eye lens just enough so that the resulting focal length when the eye is relaxed matches the distance to the back of the retina.

Astigmatism
• This occurs when the focal length for the cornea and the eye's lens for an object oriented in some direction is not the same as for another located in a perpendicular direction.
• The eye cannot bring the vertical and horizontal lines in a ‘+’ symbol in sharp focus at the same time. (The axis of differing focal length need not be exactly horizontal and vertical).
• The problem is that the cornea of the eye lens is not symmetrical. The solution is to use eye glasses whose lenses are not symmetrical in a complementary way.
• The cylindrical lens may be combined with an additional positive or negative lenses.
Decreased accommodation
• This condition typically occurs in middle-aged people.
• The eye muscles gradually weaken with age, so that the range or accommodation is decreased.
• People with this condition cannot bring both near objects and far objects into focus.
• The weakening of the eye muscles often causes the focal length of the eye lens to increase as well so that many people of middle age tend to become far sighted.
• Since the problem is adequate accommodation, no single lens can correct it and people with this problem usual needs bifocals.
• Bifocals are glasses with two different lens strengths, one for near and one for distant objects.
• The usual arrangement is that the bottom half of the lens is the near strength and the top half is the far strength.
The Correction of the Defects of Human Eye
Describe the correction of the defects of human eye
Myopia is common name for impaired vision in which a person sees near objects clearly while distant objects appear blurred. In such a defective eye, the image of a distant object is formed in front of the retina and not at the retina itself. Consequently, a nearsighted person cannot focus clearly on an object farther away than the far point for the defective eye.
This defect arises because the power of the eye is too great due to the decrease in focal length of the crystalline lens. This may arise due to either
1. Excessive curvature of the cornea, or
2. Elongation of the eyeball.

Correction: This defect can be corrected by using a concave (diverging) lens. A concave lens of appropriate power or focal length is able to bring the image of the object back on the retina itself.
Farsightedness, also called hypermetropia, common name for a defect in vision in which a person sees near objects with blurred vision, while distant objects appear in sharp focus. In this case, the image is formed behind the retina.
This defect arises because either
1. the focal length of the eyelens is too great, or
2. the eyeball becomes too short, so that light rays from the nearby object, say at point N, cannot be brought to focus on the retina to give a distinct image.
Correction: This defect can be corrected by using a convex (converging) lens of appropriate focal length. When the object is at N’, the eye exerts its maximum power of accommodation. Eyeglasses with converging lenses supply the additional focusing power required for forming the image on the retina.

THE HUMAN EYE AND THE LENS OF THE CAMERA

The camera
1. The eye and the camera have a convex lens which forms a real and inverted image of an object.
2. The eye and the camera are blackened inside to prevent internal reflection. Rays of light which are not received on the retina or camera film are absorbed by the choroid layer of the eye or the black surface inside the camera.
3. The eye can regulate the amount of light that passes through the crystalline lens by using pupil while in a camera the diaphragm regulates light.
4. In the eye the image is formed in the retina while in the camera the image is formed on the photographic plate.
5. The eye can change the focal length of its lens by the contraction and relaxation of the ciliary muscles. In this way the eye can focus objects at different distance. In a camera objects at different distance are focused on by moving the lens forwards and backwards.

[11/22/18]   KINETIC THEORY OF MATTER:
The kinetic theory of matter describes the physical properties of matter in terms of the behavior of its component atoms or molecules.
It states that,"All matter is made up of very small particles that are in constant motion".
The more the heat energy the particles possess the faster they move.The theory can be used to explain the properties of solids, liquids and gases as well as changes in state of matter.The kinetic theory is also known as the molecular theory of matter.
In solid,the particles are arranged close together in a regular pattern and vibrate in fixed positions.These particles have the lowest value of kinetic energy.
In liquid,the particles are still close together but in an irregular arrangement.Unlike those in a solid, the particles in liquid move about and are able to slide past one another.
In a gas,the particles are far apart moving rapidly and bouncing off the walls of their container.

[10/29/18]   THE HUMAN EAR:
The human ear responds to vibrations of air caused by oscillating bodies.However, oscillating bodies can make vibrations ranging from small frequencies to very high frequencies in the magnitude of megahertz (A hertz is cycles per second,unit of frequency and 1MHz=10^6Hz).The human ear isn't capable of responding to all ranges of frequencies,but the range of human ear can respond, called the audible range is from 20Hz to 20KHz.That is,20Hz is the lowest and 20KHz is the highest limit, though there might be some people with slightly different limits from this.
Air vibrations impinging on the pina/ear lobe are directed through the channel to the ear drum which is set in vibrations.The vibrations of the ear drum are taken up by the three auditory ossicles called hammer,anvil and stirrup which are arranged such that they increase the force of vibration because they have greater mechanical advantage.These ossicles,which are in the middle ear cause the oval window to vibrate violently, there by setting up the fluid in the cochlea or inner ear to oscillate.There is a membrane covering the top part of the cochlea running from the oval window winding up to almost its tip on which the fluid oscillates.The membrane has erect fibres of different lengths all along its surface.All the fibres are connected to the auditory nerve by nerves.When the fluid oscillates, the fibres also oscillate but each fibre can respond to certain frequencies only.The message from these fibres is collected in a form of electric pulse to the brain via the auditory nerve.If some fibres are removed the person becomes deaf to certain frequencies corresponding to the removed fibres.
Note that the vibrations of the fluid are damped by the round window which is at the extreme end of the lower part of the inner ear.

[09/26/18]   Start to make a difference with the world around you, focus on one thing at a time and start with the one closest to you

[09/16/18]   Take note of the setbacks and adjust to them but don't expand them by making them a bigger part of your life.Everyday brings new lessons and possibilities, there is always a way to take the next step forward if not when then how you may endure and proceed.

06/09/2018
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TED-Ed

How knowing more than one language can actually change the way your brain looks and works:

10/07/2018

Spirit Science

A great affirmation. Can you wholeheartedly affirm this to yourself?

Artwork by Archan Nair

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Biology WORLD

B.sc classes start

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Uplift Connect

The only person you should try outdo is the old YOU.

medicalxpress.com 20/06/2018

Cell type and environment influence protein turnover in the brain

medicalxpress.com Scientists have revealed that protein molecules in the brain are broken down and replaced at different rates, depending on where in the brain they are.

phys.org 17/04/2018

Engineering a plastic-eating enzyme

phys.org Scientists have engineered an enzyme which can digest some of our most commonly polluting plastics, providing a potential solution to one of the world's biggest environmental problems.

phys.org 12/04/2018

'Water-in-salt' electrolyte yields stable cathode for lithium-air battery operations

phys.org Harnessing the full electrochemical power of lithium-oxygen batteries requires an efficient, more stable electrolyte. Researchers from Boston College have applied a "water-in-salt" electrolyte that enables stable lithium-air battery operation, offers superior long cycle lifetimes and presents a plat...

medicalxpress.com 12/04/2018

Study reveals every bowel tumor and bowel cancer cell have unique genetic fingerprints

medicalxpress.com New research on bowel cancer has shown that every tumour is different, and that every cell within the tumour is also genetically unique. In the first study of its kind, researchers from the Wellcome Sanger Institute, UK and Hubrecht Institute (KNAW) in Utrecht, The Netherlands, used the latest singl...

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