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Light waves can also interact with each other by interference , creating complex patterns of motion. Dropping two pebbles into a puddle causes the waves on the puddle’s surface to interact, creating complex interference patterns. Light waves can interact in the same way.

In addition to interfering with each other, light waves can also interact with small objects or openings by bending or scattering. This is called diffraction . Diffraction is larger when the object is smaller relative to the wavelength of the light (the distance between two consecutive peaks of a light wave). Often, when waves diffract in different directions around an obstacle or opening, they will interfere with each other.

  • If a light wave has a long wavelength, is it likely to have a low or high frequency?
  • If an object is transparent, does it reflect, absorb, or transmit light?

Lenses and refraction

In the context of microscopy, refraction is perhaps the most important behavior exhibited by light waves. Refraction occurs when light waves change direction as they enter a new medium ( [link] ). Different transparent materials transmit light at different speeds; thus, light can change speed when passing from one material to another. This change in speed usually also causes a change in direction (refraction), with the degree of change dependent on the angle of the incoming light.

Picture a shows a light beam aimed at a piece of glass. When the light beam hits the transparent glass material it bends by approximately 45°. This bent light ray is the refracted ray. The opaque material which the glass is sitting upon does not have any light shining through it. Diagram b shows an arrow labeled incident ray pointing at a 45° angle down towards a shaded region. At the point where the incident ray reaches the shaded region, two other arrows begin. One of these arrows points at a 90° angle from the incident ray (and away from the shaded region) and is the reflected ray. The second arrow continues through the shaded region but at a slightly bent angle from the incident ray. This second arrow is the reflected ray.
(a) Refraction occurs when light passes from one medium, such as air, to another, such as glass, changing the direction of the light rays. (b) As shown in this diagram, light rays passing from one medium to another may be either refracted or reflected.

The extent to which a material slows transmission speed relative to empty space is called the refractive index of that material. Large differences between the refractive indices of two materials will result in a large amount of refraction when light passes from one material to the other. For example, light moves much more slowly through water than through air, so light entering water from air can change direction greatly. We say that the water has a higher refractive index than air ( [link] ).

A photo shows a pole being placed in water. The pole looks like it bends where it hits the water.
This straight pole appears to bend at an angle as it enters the water. This optical illusion is due to the large difference between the refractive indices of air and water.

When light crosses a boundary into a material with a higher refractive index, its direction turns to be closer to perpendicular to the boundary (i.e., more toward a normal to that boundary; see [link] ). This is the principle behind lenses . We can think of a lens as an object with a curved boundary (or a collection of prisms) that collects all of the light that strikes it and refracts it so that it all meets at a single point called the image point (focus) . A convex lens can be used to magnify because it can focus at closer range than the human eye, producing a larger image. Concave lenses and mirrors can also be used in microscopes to redirect the light path. [link] shows the focal point (the image point when light entering the lens is parallel) and the focal length (the distance to the focal point) for convex and concave lenses .

Questions & Answers

can you please differentiate between vacuoles and inclusion bodies
Noor Reply
vacuoles consists of watery solution called cell sap while bodies are organelles
Prince
5 difference please
Noor
Archaea is an odd type of bacteria that live in extreme environments; high salt, high temperature etc. usually called extremophiles.
Danesia Reply
you know anyone that has delt with enterobacter agglomerans.
Vernon
it is a type of gram negative bacteria and its ubiquitous mostly isolated from plant stuffs and also from faecal material of animals. I heard the name pantoea . it is bacillus in structure.
Sujan
What are the classification of microorganisms
Portia Reply
Basic classification are eukaryotic and prokaryotic..
micro organisms are classified into three namely: Archaea, eukaryote and prokaryotic organisms
Blandine
Yay that's right
what is archaea
Ateeq
I've got an issue with the message view
Frank Reply
Is there any effective way to learn microbiology.
Frank Reply
I have some basic knowledge of biology. I mean i'm totally beginner in that field.
Frank
Assuming that i'm interested in neuroscience. What is the best way to master that particular subject.
Frank
Hi
Can you wait me just a minute
Iam apologies for guidance you in neuroscience.. I'm not physician.. I'm microbiologist
My pleasure to join to you
Let's begin a conversation
Frank Reply
What would be saying
?
Akram
do you know anything about microbiology
diana
I have so much studying to catch up on🙄
Britnee
any study tips
Britnee
Yas of course
What would you like to know
well i'm studying Pharmacy second year and i just started With Microbiology
diana
if you have any basics to tell us 🤷🏻‍♀️ would be helpful
diana
Yas, first you must know that you will have a very easy lecture..
In second stage you will try to learn the type of microbiology
A simple definition for microbiology
In second stage you will try to learn the type of microbiology.. you must learn the bacteria..its structure.. Classification of bacteria according to shape..
It's so easy
What triggers the natural killer cells
jenipher Reply
microbiology is the study of science which deals with study of microorganism e.g .virus,bacteria
sufian Reply
microbiology is a branch of science that deals with invisible microorganisms.
Abdinur
microbiology is the branch of science which deals with the study of organisms too small to be seen with the naked eye
Andrre
what is microbiology
Safwan Reply
history of microbiology
julie
give all details about cell
Samim Reply
Give me another names for all hypersensitivity
Don Reply
Give me the modern father of microbiology
Don
Antonie van Leeuwenhoek
RITU
Louis pasteur is father of modern microbiology Antonie van Leeuwenhoek is only the father of microbiology
Sujan
Antonie van Leeuwenhoek was the first person to observe the mos. whereas pasteur is the one who described about the vaccine , pasteurization etc.
Sujan
what is the virulence factor
mukhtar Reply
is the abilityof pathogen that cause disease
mary
classification of bacteria
Divya Reply
are classified into 5 as follow 1= bacilli 2= vibro 3= spirilla 4= cocci 5= spirochaetes.
Abdulkareem
this one is on the basis of morphological structure
Sujan
gram positive and gram negative according to gram staining
Sujan
u can find on the basis of temperature resistance and oxygen tolerance
Sujan
good
ANAS
on basis of oxygen requirement they could be categorized as Aerobic anaerobic facultative aerobes microaerophilic
ANAS
bacteria are classified into the three type according to their shape 1.Round cocci 2.Rod bacilli 3. spiral
mukhtar
sorry to say but for microbes there is no facultative aerobes instead it must b facultative anaerobic and obligatory anaerobic, aerotolerant
Sujan
Which ones are the microaerophilic
Godwin
what is the difference between krebs cycle and calvin cycle
Baye Reply

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Source:  OpenStax, Microbiology. OpenStax CNX. Nov 01, 2016 Download for free at http://cnx.org/content/col12087/1.4
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