Light and sound both travel as waves. Light can travel through a vacuum whereas sound must travel through a solid, liquid or gas. Both follow the laws of reflection and refraction. Show
Light rays change direction when they reflect off a surface, move from one transparent medium into another, or travel through a medium whose composition is continuously changing. The law of reflection states that, on reflection from a smooth surface, the angle of the reflected ray is equal to the angle of the incident ray. (By convention, all angles in geometrical optics are measured with respect to the normal to the surface—that is, to a line perpendicular to the surface.) The reflected ray is always in the plane defined by the incident ray and the normal to the surface. The law of reflection can be used to understand the images produced by plane and curved mirrors. Unlike mirrors, most natural surfaces are rough on the scale of the wavelength of light, and, as a consequence, parallel incident light rays are reflected in many different directions, or diffusely. Diffuse reflection is responsible for the ability to see most illuminated surfaces from any position—rays reach the eyes after reflecting off every portion of the surface. law of refraction When light traveling in one transparent medium encounters a boundary with a second transparent medium (e.g., air and glass), a portion of the light is reflected and a portion is transmitted into the second medium. As the transmitted light moves into the second medium, it changes its direction of travel; that is, it is refracted. The law of refraction, also known as Snell’s law, describes the relationship between the angle of incidence (θ1) and the angle of refraction (θ2), measured with respect to the normal (“perpendicular line”) to the surface, in mathematical terms: n1 sin θ1 = n2 sin θ2, where n1 and n2 are the index of refraction of the first and second media, respectively. The index of refraction for any medium is a dimensionless constant equal to the ratio of the speed of light in a vacuum to its speed in that medium. By definition, the index of refraction for a vacuum is exactly 1. Because the speed of light in any transparent medium is always less than the speed of light in a vacuum, the indices of refraction of all media are greater than one, with indices for typical transparent materials between one and two. For example, the index of refraction of air at standard conditions is 1.0003, water is 1.33, and glass is about 1.5. The basic features of refraction are easily derived from Snell’s law. The amount of bending of a light ray as it crosses a boundary between two media is dictated by the difference in the two indices of refraction. When light passes into a denser medium, the ray is bent toward the normal. Conversely, light emerging obliquely from a denser medium is bent away from the normal. In the special case where the incident beam is perpendicular to the boundary (that is, equal to the normal), there is no change in the direction of the light as it enters the second medium.
electromagnetic radiation: Visible radiation Visible light is the most familiar form of electromagnetic radiation and makes up that portion of the spectrum to which... double convex lens Snell’s law governs the imaging properties of lenses. Light rays passing through a lens are bent at both surfaces of the lens. With proper design of the curvatures of the surfaces, various focusing effects can be realized. For example, rays initially diverging from a point source of light can be redirected by a lens to converge at a point in space, forming a focused image. The optics of the human eye is centred around the focusing properties of the cornea and the crystalline lens. Light rays from distant objects pass through these two components and are focused into a sharp image on the light-sensitive retina. Other optical imaging systems range from simple single-lens applications, such as the magnifying glass, the eyeglass, and the contact lens, to complex configurations of multiple lenses. It is not unusual for a modern camera to have a half dozen or more separate lens elements, chosen to produce specific magnifications, minimize light losses via unwanted reflections, and minimize image distortion caused by lens aberrations.
In order to continue enjoying our site, we ask that you confirm your identity as a human. Thank you very much for your cooperation. In optics, angle of incidence can be defined as the angle between a ray incident on a surface and the line perpendicular to the surface at the point of incidence (called as normal). To understand the angle of incidence, we have to first look into the concept of reflection of light. We all know that when a ray of light hits a polished surface like a mirror, it is reflected back. Here are some key points to make you understand the concept of angle of incidence easily. What is Angle of Incidence?The incident ray and reflected ray form two angles at the point of incidence:
Angle of Incidence FormulaThe angle of incidence is equal to the reflected angle through the law of reflection. The angle of incidence and the angle of reflection is always equal, and they are both on the same plane along with the normal. Examples of Angle of IncidenceExample 1: Consider a light ray which is incident on a flat surface such that it makes an angle of 10° with the surface.
Solution:
Example 2: The angle at which the light ray strikes the reflective plane surface is 56°. Find
Solution: Consider the below diagram to answer the questions:
What is the Relationship between the Angle of Incidence and Angle of Reflection?When light passes from one medium to another with different densities, its path gets deviated. This phenomenon is called the refraction of light. Like a reflection, there are similar components in refraction too. They are:
The angle formed at the point of incidence between the incident ray and the normal is called the angle of incidence. The angle formed between the refracted ray and the normal is called the angle of refraction. The relationship between the angle of incidence and angle of refraction is explained by Snell’s law, which states that the ratio of the sine of the angle of refraction and the sine of the angle of incidence is always constant and equivalent to the ratio of phase velocities of the two mediums it is passing through.
In total internal reflection, when the angle of incidence is equal to the critical angle, the angle of reflection will be 90°.
The angle of incidence is equal to the angle of reflection because the light ray selects the shortest path to reach the destination. This behaviour of light is known as Fermat’s principle. The same behaviour is shown by the light ray when it gets reflected from the plane surface. Therefore, the angle of incidence and the angle of reflection are equal.
The ray of light is incident normally on a plane mirror, which means that the angle of incidence is 0° and not 90° degrees. Therefore, the angle of reflection is 0°.
The angle of reflection decreases when the angle between the incident ray and the mirror is increased. This is because of the glancing angle of incidence. The glancing angle of incidence is the angle formed between the incident ray and the mirror. Also, the sum of glancing angle of incidence and the angle of incidence angle is 90°. So, an increase in the glancing angle results in the decrease of incidence angle. We know that, angle of incidence is equal to angle of reflection. Hence, the angle of reflection decreases.
The given statement is true. That is, the laws of reflection hold good for all types of mirrors. To learn about other Physics – related topics download BYJU’S – The Learning App.
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