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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

what is fermentation example ?
Sonal Reply
is proceess in which an agent couses of an oganic substances breakdown into simpler substance,especially in aneorobic breakdown of suger into alcohol.
Okashat
is it better to study microbiology and then medicine it makes no difference to go directly to medicine?
Jessee Reply
Dray's mathdme cell wall konse color k hote he
Jinal Reply
what is dray's mathdme cell wall
Prabhat
I confused. please help me
Karen
just confused
Raj
l don't understand it please explain it for me.
Karen Reply
epitopes are present on the surface of
Rohit Reply
at the tip of variable region on the antibody...where antigen and antibody binding sites combine...
Fiza
The term that is used refer to moving microbes under a microscope are referred to as?
Lee Reply
Members of the genus Neisseria cause which of the folowing human diseases?
Farah Reply
genital infections
Kamaluddeen
gonorrhoea
sandip
gonorrhoea
Jessee
4. Which of the following specimens should not be refrigerated? a. Urine b. Urogenital swab
Zahraa Reply
urine
Muuse
urine
Agatha
Urine
Tean
urine
Yasser
Urine
Ebtehal
urine
anamika
urine
Puja
urine
Inemesit
urine
Samuel
Urine
Muhammad
Details about McConkey agar
Muhammad
urine
SK
urine
what is bacteria
anamika Reply
a member of large number of unicellular microorganism which have cell wall but lack of cell organelles an oranised nucleus including somewhat can cause disease
Sukhdeep
Bacteria are usually composed of one cell onl to that are neither plants nor animals, microscopic, that may cause diseases or may be beneficial(in gut)... it depends upon their weapons. Nearly all animal life is dependent on Bacteria for their survival
Fiza
thanks
anamika
what factor make bacteria colony large and how could we sterlise it in large scale
fatty
nutrient concentration temp gaseous conc ph ion or salt concentration mositure condition factors contribute to make large colony. by autoclaving we will sterilize bactetia
Sukhdeep
Colony is actually visible growth of Bacteria that is as a result of suitable environment for growth i.e optimal conditions for growth, temperature, moisture etc. there're many methods to get rid of bacteria. If We stop giving them optimal conditions for living Bacteria will die soon .
Fiza
what's the difference between an antigen and a pathogen?
Pathogens are organisms that cause disease in other organisms whereas Antigen is a part of a pathogen that triggers the immune response..
Rajat
so it is the antigen that dendritic cells present to the T cells and not the pathogen itself?
no no antigen are the west product or part of the pathogen. in such case bacteria it self fight with over immune response & in another case bacteria release antigens
vasava
& other antigen like pollan grain, dust particles etc.....
vasava
pathogen are microbes that can infect the body and causw illness....antigens are the part of pathogens that alert the body to an infection
Sukhdeep
antigen is a part of blood and pathogen is foreign particle which causes diseases
Yogyata
antigen could be non microorganism.... where as pathogen is mixroorganism
tadesse
Thanks
Karen
a pathogen is a disease causing organism while an antigen is a protein in the white blood cells which combats pathogens.
Jessee
what type of widal test
sobhit Reply
this test determine for typhoid in this test if H,O antigen are present that indicate the positive test bac. are salmonella typhy
vasava
what h.o denotes
Iqra
o: body of bacteria, h: flagellate
Explain Mould
Chinenye Reply
Explain mycoses and it's classification
Chinenye
why do we have hiccups?
Manisha Reply
shakey diaphragm
Curlisse
The antibody binding site is formed primarily by:
Asalla Reply
How many types of MICROORGANISMS do we have?
Hope Reply
Hello friends
Hope
microorganisms are divided into seven type Bacteria archaea protozoa algae fungi virus and multicellular animal parasites
Raj

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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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