<< Chapter < Page Chapter >> Page >
Diagram a (prism) shows a clear pyramid with light entering one surface. The light leaving the other surface is bent and is the refracted light. A dotted line indicates the path the original light beam would have taken had it not bent. The region above the dotted line is labeled high refractive index; the region below the line is labeled low refractive index. Diagram b (convex lens) shows a lens with a bulge in the center. Light enters one either side of the dome and is focused to a point past the lens and in line with the center of the dome. The point at which the light focuses is the focal point; the distance from the focal point to the center of the lens is the focal length. Diagram c (concave lens) shows a lens that curves inward on either side. Light entering this lens is bent outwards, away from the center of the lens’s curve. A dotted line shows the linear path backwards for each of the bent light beams. The point at which all the dotted lines meet (which is on the other side of the lens) is the focal point.
(a) A lens is like a collection of prisms, such as the one shown here. (b) When light passes through a convex lens, it is refracted toward a focal point on the other side of the lens. The focal length is the distance to the focal point. (c) Light passing through a concave lens is refracted away from a focal point in front of the lens.

The human eye contains a lens that enables us to see images. This lens focuses the light reflecting off of objects in front of the eye onto the surface of the retina, which is like a screen in the back of the eye. Artificial lenses placed in front of the eye (contact lenses, glasses, or microscopic lenses) focus light before it is focused (again) by the lens of the eye, manipulating the image that ends up on the retina (e.g., by making it appear larger).

Images are commonly manipulated by controlling the distances between the object, the lens, and the screen, as well as the curvature of the lens. For example, for a given amount of curvature, when an object is closer to the lens, the focal points are farther from the lens. As a result, it is often necessary to manipulate these distances to create a focused image on a screen. Similarly, more curvature creates image points closer to the lens and a larger image when the image is in focus. This property is often described in terms of the focal distance, or distance to the focal point.

  • Explain how a lens focuses light at the image point.
  • Name some factors that affect the focal length of a lens.

Electromagnetic spectrum and color

Visible light is just one form of electromagnetic radiation (EMR) , a type of energy that is all around us. Other forms of EMR include microwaves, X-rays, and radio waves, among others. The different types of EMR fall on the electromagnetic spectrum, which is defined in terms of wavelength and frequency. The spectrum of visible light occupies a relatively small range of frequencies between infrared and ultraviolet light ( [link] ).

A series of scales indicate that the image shows the lowest wavelength (10 superscript -18 m) on the left and the highest wavelength (10 superscript 6 m) on the right. The frequencies range from over 10 superscript 24 Hzon the left to 1 Hz on the right. The energies range from 10 superscript 12 ev on the left to 10 superscript -12 on the right. The types of radiation listed above these scales (from left to right) is: cosmic radiation, gamma rays, X-rays, ultra-violet, visible, infrared, Terahertz radiation, radar, television and radion broadcasting, and AC circuits. The visible light portion of the spectrum is pulled out and shows blue light at 400 nm, green light at 500 nm, yellow light at 600 nm, and red light at 700 nm.
The electromagnetic spectrum ranges from high-frequency gamma rays to low-frequency radio waves. Visible light is the relatively small range of electromagnetic frequencies that can be sensed by the human eye. On the electromagnetic spectrum, visible light falls between ultraviolet and infrared light. (credit: modification of work by Johannes Ahlmann)

Whereas wavelength represents the distance between adjacent peaks of a light wave, frequency, in a simplified definition, represents the rate of oscillation. Waves with higher frequencies have shorter wavelengths and, therefore, have more oscillations per unit time than lower-frequency waves. Higher-frequency waves also contain more energy than lower-frequency waves. This energy is delivered as elementary particles called photons. Higher-frequency waves deliver more energetic photons than lower-frequency waves.

Photons with different energies interact differently with the retina. In the spectrum of visible light, each color corresponds to a particular frequency and wavelength ( [link] ).The lowest frequency of visible light appears as the color red, whereas the highest appears as the color violet. When the retina receives visible light of many different frequencies, we perceive this as white light. However, white light can be separated into its component colors using refraction. If we pass white light through a prism, different colors will be refracted in different directions, creating a rainbow-like spectrum on a screen behind the prism. This separation of colors is called dispersion , and it occurs because, for a given material, the refractive index is different for different frequencies of light.

Questions & Answers

what is pathogenic
kelvin Reply
biological pathogen is anything that can produce disease. a pathogen may also be referred to as an infectious agent, or simple a germ.
Dejene
Thanks
kelvin
explain 3 points why gender is relevant to health.
kelvin
wat causes sor throat
Ezeama Reply
Streptococcus
Rajat
Streptococcus
Panda
Gram positive
shamim
streptococcus pyrogenes
Sherma
group A streptococcus pyogenes. But not the only one.
Carlos
does the bac of s.aures gives choronic diseas in bone?
Elyas
causes virus bac group A strep allergies smoking
Elyas
truth also virus
Shania
what z microbiology
Mwelwa Reply
microbiology is all about the scientific study of microorganisms, their life changes, their life span, structural punctuality and their phenomenon.
Ridwan
thanks
micah
Best scope in microbiology
Rahul
wat abut skin
Elyas
whatis scope
Amare
what is scope
Funmi
what happened when someone died and what happened to the blood
Franca Reply
nice question
Attari
when you die you have no memory and the blood dry off
Falere
what microorganisms is all about?
Ridwan
And how many does the microorganisms is classified?
Ridwan
How are microbs organized
Saskia
what is endoparasites and exo parasite and their example
OGEDE Reply
Endo : inside the body Exo/ecto : outside or on the body
Paul
examples please
OGEDE
Louse for exo/ecto Helminths (worms) for endo
Paul
what's prokaryotic
mohaiminul Reply
A prokaryotic cell is a cell with no membrane bounds organelles
Paul
what are the main effect of parasite?
yunusa Reply
nutritional group of micro organism
Mana Reply
what are the charateristic bacteria, eukaryotes, and viruses have in commom
Ami Reply
what type of bacteria ismor serious
Amare
D N A ar purno rup ki
Ruba Reply
বাংলায় দেখবো DNA এর পূর্রন্যরুপ কি
Ruba
what's microbiology
micah
micro biology is the study of micro organisms,those being unicellular multicellular or a cellular
aniisha
deoxyribonucleic acid is a long molecule that contains our unique genetic code.
aniisha
Does the parasite/parasitology are under microbiology or not
yunusa
Define bacteria
Kainat
Bacteria are a type of biological cell & they constitute a large domain of prokaryotic microorganisms.
raisa
what kind of microbiology
Mira
hello what is main function of T and B cells
Ishaq Reply
T cells are involved in cell-mediated immunity while B cells are primarily responsible for humoral immunity (relating to antibodies)
Janet
what is hepatitis B
Sunday
it's viral infection that attacks the liver and can cause both acute and chronic diseases. the virus is most commonly transmitted from mother to child during birth and delivery, as well as through contact with blood or other body fluids...
Dejene
What are fundamental experiment of microbiology?
Lucky Reply
study of microscopic organisms, unicellular and multicellular
Falere
what are the characteristics of bacteria, viruses, and eukaryotes
Ami
bacteria-are living organism. contain a peptidoglycan/lipopolysaccharide cell wall. VIRUS-are considered as organic structure which interact with living organism don't have acell wall. they have many differents like bacteria size -large(1000nm) virus size-smaller(20-400nm). bacteria ribosomes presen
Dejene
virus ribosomes absence. bacteria living organism. virus b/n living and non-living things
Dejene
eukaryotic cell has a true membrane bond nucleus and has other membranous organelles that allow for compartmenalization of function
Dejene
This answer is wrong
Jeffrey Reply
who discovered the growth curve
Joy Reply
Example of coccus bacteria
Nweke Reply
staphylococcus aureus
Elton
MRSA any bew information
Satish
pl. read any new information about MRSA
Satish
Any stru tural finding about novel corona virus
Satish

Get the best Microbiology course in your pocket!





Source:  OpenStax, Microbiology. OpenStax CNX. Nov 01, 2016 Download for free at http://cnx.org/content/col12087/1.4
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Microbiology' conversation and receive update notifications?

Ask