Introduction:
Scientists and engineers have been able to enhance our lifestyles by understanding and using the Laws, Concepts and Principles of Optics and how they are applied in Optical Instruments. The key concepts are:
a. Lights as a form of electromagnetic radiation
Electromagnetic radiation is a term used to describe a pair of electric and magnetic fields that promulgate together at the speed of light. This means that light holds electric and magnetic components. The accelerated movement of electric charges emits radiation. This radiation is visible to us as light.
Figure 1: electromagnetic waves
Time-varying electric fields can bring magnetic fields and vice-versa. Since both fields generate each other, they occur jointly and therefore, propagate as electromagnetic waves.
The electromagnetic radiation of light is a small part of the electromagnetic spectrum.
Like all wave phenomena, radiation is considered by its wavelength and its frequency f. Electromagnetic radiation promulgates at the speed of light c. The equation is: .
Application such as the sun emits most of its radiation in the visible range which our eyes recognize as the color of rainbow.
b. Law of reflection
The law of reflection states that when a ray of light strikes a plane mirror, the light ray is reflected off the mirror as such that the angle of reflection is equal to incidence angle. The diagram below illustrates the law.
Figure 2: angle of reflection=angle of incidence
In the diagram, the light approaching the mirror is the incident ray and the light leaving the mirror is the reflected ray. The line perpendicular to the mirror is the normal line. The angle between the incident ray and the normal line is the angle of incident and the angle of r...
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Rainbow color components are evident through dispersion of visible light and total internal reflection in prisms.
6. Refraction in lenses
The refractive index of lens is larger than air therefore refraction in lenses occurs differently. It happens when light moves parallel to the normal and is refracted through the focal point. If a ray passes through the optical center of the lens, the ray would continue without being refracted. The optical direction is the point on the normal where the incident direction of a ray is parallel to the emergent direction.
Figure 13: converging lens
In a convex lens, the rays are parallel to the axis (normal) and cross each other at a single point on the focal point. This is called converging lens.
Figure 14: diverging lens
In a concave lens, the light rays bend away from the normal. This is known as diverging lens.
projected its rays through the tinted glass... But in the western or black chamber the effect of the
If you are farsighted, your eye does not have enough focusing power — light rays fail to form a focus point by the time they reach the retina. Contact lenses rectify hyperopia by converging light rays, which increases the eye's focusing power. This moves the eye's focus point ahead, onto the retina where it belongs. To correct farsightedness the contact lens is thicker in the center and thinner at the edges. These lenses are known as convex.
This is a representation of the eye's lens system. This eye has no eye condition, such as nearsightedness or farsightedness, and the lens is drawn in its relaxed position. The light rays are focused appropriately on the retina. The thickness of the cornea is 0.449 mm, the distance from the cornea to the lens is 2.
lies in the same plane as the incident ray and normal at the point of
The first Fresnel Lens date back to 1822 when a French physicist by the name of Augustin Fresnel wanted to make our bodies of water safer for sailors throughout the world. The Fresnel Lens originally were a type of compact lens created by Fresnel for lighthouses. A Fresnel lens replaces the curved surface of a conventional lens with a series of concentric grooves, molded into the surface of a thin, lightweight plastic sheet (“Fresnel Lenses”). The Fresnel Lens were beneficial for lighthouses because they have the ability to capture more oblique light which allowed lighthouses that used them to be seen from greater distances. Fresnel’s lens resembles a giant beehive with a complex system of multi-faceted glass prisms mounted in a brass framework.
Light is both part particle and part wave. Light is “the electromagnetic radiation that may be perceived by the human eye”. It consists of photons, which are massless bundles of concentrated electromagnetic energy. Light’s lower frequency is red, and the higher frequency is blue. Like sound, light has frequencies humans can’t detect. Ultraviolet light is at a frequency higher than violet, and infrared is at the frequency lower than the red of visible light. We get UV (ultraviolet) rays from the sun, and infrared is used in night vision to see better.
X-rays and gamma ray photons are part of the electromagnetic spectrum. The twin nature of electromagnetic radiation is used to justify the wave and its behavior. A photon is a bundle of energy that can be identified by the equation E = hv. Where h is the planks constant and v is the frequency. The frequency is equal to the speed of light 3x10 8 divided by the wavelength. Therefore, high-energy radiations have a short wavelength and a high frequency.
Electromagnetic waves are waves that can propagate even though there is no medium. A magnetic field that changes with time can generate an electric field that also changes with time, and an electric field that changes with time can also produce a magnetic field. If the process is continuous it will produce a magnetic field and electric field continuously. If these magnetic fields and electric fields simultaneously propagate (spread) in space in all directions then this is a symptom of the wave. Such a wave is called an electromagnetic wave because it consists of an electric field and a magnetic field that travels in space.
Spectrum refers to the electromagnetic spectrum, which is the range of frequencies through which electromagnetic radiation travels. Electromagnetic radiation is the energy that travels at the speed of light in waves as a stream of photon particles. This form of energy encompasses radio waves, microwaves, visible, nonvisible light, X–rays and gamma rays, and these classifications are based upon the frequency at which the energy travels (see figure 1). In order to refer to a specific portion, also called a band, of the electromagnetic spectrum, one uses Hertz (Hz) as the unit of measurement. Figure 1: Spectrum has an abundance of practical applications.
Radiation is the process of emitting radiant energy in the form of waves or particles that travels through a medium or space. Radiation sources can be divided into two main categories which are non-ionizing radiation and ionizing radiation. Non-ionizing radiation includes natural background sources and man-made sources. The sun is one of the major background sources of radiation. It sends out ultraviolet rays that penetrate and damage human skin by causing sunburn. Certain minerals that make up part of the earth contain the radioactive elements. The levels may typically be in the range of 15 to 60 counts per minute that will vary depending upon one’s location on the earth, and the efficiency of the radiation sensor used.
Perhaps the greatest contribution to the astronomy was the intervention of the reflecting telescope. Further, he analyzed the properties of glass and came to the conclusion that refracting telescopes would always suffer from the noticeable aberrations. Further, the fundamental problem was the chromatic aberration. It arises from the prism-like effect, as light passes through a lens and is bent. Besides, every wavelength of the light is bent by the different amount. In essence, the red light appears to be bent more than the blue
Nature of wave: It is an electromagnetic wave as it does not necessarily require a medium for p...
Refraction of Light Aim: To find a relationship between the angles of incidence and the angles of refraction by obtaining a set of readings for the angles of incidence and refraction as a light ray passes from air into perspex. Introduction: Refraction is the bending of a wave when it enters a medium where it's speed is different. The refraction of light when it passes from a fast medium to a slow medium bends the light ray toward the normal to the boundary between the two media. The amount of bending depends on the indices of refraction of the two media and is described quantitatively by Snell's Law. (Refer to diagram below)
So how do we get to see a rainbow in the sky? First condition that must be fulfilled is that the sun must be shining, more to that, the sun must be behind you and raindrops must be present in the sky. When these three conditions are present, then the sun will shine to the little droplets that act a prism. The rays will get refracted twice, thus, producing different variety of colors. However, each drop will only produce one color thus ...
Light can be classified as a form of electromagnetic radiation, which includes visible light. The ‘light’ commonly referred to in everyday life belongs in this category. The electromagnetic spectrum includes other types of radiation such as gamma rays, radio waves and cosmic rays, all of which possess distinct wavelengths, frequencies and energy levels. These forms of electromagnetic radiation are not visible to the human eye but can be perceived by selected species of animals, such as bees. Figure 1 below displays the electromagnetic spectrum and provides a basic insight into the respective characteristics of different forms of radiation.