# What is Angle of incidence: Definition and 54 Discussions

In geometric optics, the angle of incidence is the angle between a ray incident on a surface and the line perpendicular to the surface at the point of incidence, called the normal. The ray can be formed by any wave: optical, acoustic, microwave, X-ray and so on. In the figure below, the line representing a ray makes an angle θ with the normal (dotted line). The angle of incidence at which light is first totally internally reflected is known as the critical angle. The angle of reflection and angle of refraction are other angles related to beams.
Determining the angle of reflection with respect to a planar surface is trivial, but the computation for almost any other surface is significantly more difficult. The exact solution for a sphere (which has important applications in astronomy and computer graphics) is treated in Alhazen's problem.

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1. ### I Tilted plane wave through a 2 lens system

I have 2 lenses. L1 and L2 with focal lengths f1=910mm and f2=40mm, respectively. They are separated by a distance d=f1+f2. The magnification of the system is M1=-f2/f1=.044. If I have a normally incident, collimated beam pass through my system I will have a beam, parallel to the optic axis exit...
2. ### Angle of incidence and total internal reflection

the angle of incidence at A is 40°, then why did the answer key say "angle of incidence at A is just less than 90°". it is obvious that 40° is quite far from 90° right?
3. ### I Selective filter based on angle of incidence?

I am a using a mirror to reflect an image at an angle of incidence of 10 degrees. The mirror is also at an angle of incidence of approximately 30 degrees from the viewer and it creates undesired reflections when looking at the mirror. Here is a diagram illustrating the situation. I am looking...
4. ### I What is the smallest angle of incidence necessary so that TIR occurs?

So I figure the answer is 90 degrees...but I don't feel that is what they are after?
5. ### Optics to act as a mirror or transparent medium depending on incident angle

I am looking for an optical piece that can act as a mirror when the angle of incidence is close to normal (90 degrees) but acts as a see-through glass when the angle of incidence is less than 60 degrees? Alternatively it can be a filter placed in front of a mirror that passes a lot of light at...
6. ### The refractive index of an unknown liquid

1. A light ray in dense flint glass that has an index of refraction of 1.655 is incident to the glass surface. An UNKNOWN liquid condenses on the glass's surface. Total internal reflection on the glass-liquid interface occurs for a minimum angle of incidence on the glass-liquid interface at...
7. ### Angle of Incidence, Propagation Constant and Wavelength

Homework Statement Light of free-space wavelength λ0 = 0.87 μm is guided by a thin planar film of thickness d = 3.0 μm and refractive index n1 = 1.6, surrounded by a medium of refractive index n2 = 1.4 critical angle = 61.04° n0 = 1.00 (a) Determine (i) the angle of incidence θ and (ii) the...
8. ### What is the angle of incidence?

Homework Statement A light ray shines from a diamond (n = 2.42) into water (n = 1.33), and no refraction occurs. What is the angle of incidence? 0°30°45°60° Homework Equations sin θc = nr/ni ? The Attempt at a Solution I thought that by finding the critical angle then anything above that...
9. ### Reflection and Refraction formula help

Homework Statement 2. Homework Equations 3. The Attempt at a Solution [/B] I tried to solve this question with the general formula n=sin i / sin r. 1.5 = sin 30/sin r, r = 19.4 = 19 which is option A. But option A is incorrect. Please guide me where am I wrong..
10. Q

### Plane wave angle of incidence calculation

Good afternoon! Please help me figure out the mathematics of this simple plane wave question! 1. Homework Statement 2. Homework Equations n1*sin(theta1)=n2*sin(theta2) The Attempt at a Solution I need help calculating the angle of incidence. I found the propagation vector for incidence...
11. ### Voltage output of a photodiode (solar cell)

Hi, I'm trying to figure out how the angle of incidence will affect the voltage output of a photodiode. The obvious answer that comes to my mind is that the voltage output should be proportional to the cos(α), where α is the angle of incidence of light. However, I couldn't find any...
12. ### Dielectric slab and angle of incidence

Hello! Let's consider a plane wave represented by a ray, propagating in a 2D dielectric slab. It has a medium with refractive index n_1 as its core and a medium with refractive index n_2, n_2 < n_1, as its cladding. In order for this ray to represent a mode, it must satisfy two conditions: -...
13. ### What will happen if angle of incidence on a glass slab is 0?

I have a conceptual doubt. pl help me clarify it: What will happen if angle of incidence on a glass slab is 0? will refraction take place, or reflection, or both?
14. ### I Black body, angle of incidence

I'm trying to understand the solution to an exercise. The solution claims that that the absorbed power of a black body from sunlight with an angle of incidence of ##30^\circ## is ##P=P_0\cos(30^\circ)## The reasoning here being to take the component orthogonal to the surface. However what...
15. ### Finding the angle of refraction

Homework Statement The refractive index of diamond is 2.42. A ray of light passing from the inside of a diamond into air makes an angle of incidence of 20 degrees. Find the angle of refraction. Homework Equations n = refractive index aNd = 2.42 (my book said the speed of light in a vacuum and...
16. ### Lens aligning various angle of incidence light striking it?

Assume a flat one square foot vertical plate attached 6 feet up, outside on a wall. Dozens of yards away are various solar reflectors angled to reflect sunlight onto that plate. Problem is, the plate requires to be only struck straight on at a 0 degree angle of incidence. And, all the...
17. ### Angle of incidence and refraction

Hello PF users hope all is well! I need a reminder of the formulas needed in order to get "Sine of angle of incidence" "Sine of angle of refraction" And "Index of refraction". The only information I have available now is "Angle of incidence" And "Angle of refraction" I'm guessing...
18. ### Finding angle of refraction given angle of incidence?

Can someone help me in solving this question ? my attemp is sin42/sin 90 to get the refractive index then n =sin i/sin r to get c and for b n=1/sinc
19. ### Field frequency and angle of incidence in optical waveguides

Hello! In this previous post, most replies point out that it is not possible to predict the angle of refraction (and so the frequency) at a certain interface, given the wavelength of the original signal. In particular, But when dealing with optical waveguides, it seems to be different. I am...
20. ### Antenna theory detection of angle of incidence

Assume a 2D problem. Given a linear antenna array, let's say 3 antennas distributed around the z axis, how could we extract the incidence angle of the received wave? Having 3 antennas equally spaced by λ/2 in the z axis and connected to each other, the result gain would be a function of ϑ (angle...
21. ### Refraction through an optical fiber

Homework Statement Given a "new type" of optical fiber (index of refraction n = 1.23), a laser beam is incident on the flat end of a straight fiber in air. Assume nair = 1.00. What is the maximum angle of incidence Ø1 if the beam is not to escape from the fiber? (See attached file for...
22. ### Question about solar energy: angle of incidence

My understanding is that the seasonal variation in temperature, amongst many other things, is a reflection of the Earth's tilt. Simply put, at the equator, sun rays fall "straight down" (100% vertical), and all of their energy hits the surface of the Earth. At different latitudes, these rays...
23. ### Angle of incidence and reflection

I am trying to write a java code where the user inputs the height at which a solid body approaches a sphere of radius R and outputs the angle ##\theta## at which the body bounces off the sphere. I have all my code written is just that I don't know how to derive the equation that calculates the...
24. ### Why angle of incidence equal to angle of reflection

I want to why in ray optics. Angle between incident ray and reflecting surface normal is equal to angle between reflected ray and reflecting surface normal. Simply why angle of incidence is equal to angle of reflection?
25. ### Deriving Equation Relating Angle of Incidence to the Angle of Refracti

Homework Statement Derive an equation relating the angle of incidence and the angle of refraction as light travels from air to glass. Do it in the form of Θ2/Θ1 = expression Homework Equations I think the equation to use here is Snell's law. Right? n1sinΘ1 = n2sinΘ2 n1 = nair =...
26. ### Find the Angle of Incidence for Total Internal Reflection in a Glass Sphere

Homework Statement A ray of light incident on a glass sphere (refractive index sqrt 3) suffers total internal reflection before emerging out exactly parallel to the incident ray. What was the angle of incidence? μ = refractive index of the glass sphere, i = angle of incidence, r = angle...
27. ### Need help with angle of incidence of light through a prism

Homework Statement The direction of the ray of light enters equilateral 60° glass prism normal to the surface as shown in attached image refracted index of the prism material for the violet light is 1.651 (a) What is the angle of incidence on the surface A-B? (b) Does total internal...
28. ### MHB Angle of Incidence: Subtracting 90 Degrees Explained

I do not understand why we do we subtract from 90 degrees when finding the final answer for angle of incidence?
29. ### Angle of Incidence on a spherical lens

Firstly, I'm sorry if this is incorrect or if there is a specific place for such questions but as this is neither a problem posed to me, nor something that has been taught - I have little background with which to work with but it is something I need to do for my ERT and 2 maths teachers have...
30. ### How does the eye detect the angle of incidence?

I don't really know too much about the human body, but this is my rough understanding of how vision works: light comes from a source, like the sun, it hits an object, and then if it's of the right frequency it's reflected by the object and then enters one of your two eyes, where it is refracted...
31. ### If a beam of light with an angle of incidence

Homework Statement The maximum depth of Lake Baikal, in Russia, is 1780.7 m, making it the world’s deepest freshwater lake. If a beam of light with an angle of incidence of 59.42o enters the water from the air, what is the horizontal distance between the point where the light enters the...
32. ### Waves Unit- Angle of Incidence

Homework Statement http://imgur.com/LDx7IHomework Equations http://en.wikipedia.org/wiki/Snell%27s_law The Attempt at a Solution I'm not really sure on the approach to take for this question. Since it proves 2 angles, Snell's Law could prove to be beneficial. Thanks for the help!
33. ### Find angle of incidence given deviation angle

Homework Statement A ray of light passes from air into benzene. For its deviation angle δ = |θ1 - θ2| to be 9.5°, what must be its angle of incidence? The refractive index of benzene is 1.501. Homework Equations Snell's law The Attempt at a Solution From Snell's law we have sin...
34. ### Angle of deviation and angle of incidence?

Homework Statement This is a two part problem: 11) The index of refraction for violet light in silica ﬂint glass is 1.66, and that for red light is 1.62. What is the angle of deviation for the red ray passing through a prism of apex angle 59.6◦ if the angle of incidence is 54.8◦...
35. ### Why do we measure the angle of incidence or reflection

Why do we measure the angle of incidence or reflection (or say refraction even) w.r.t normal to the surface and why not w.r.t the horizontal surface?
36. ### Measuring the angle of incidence into a fiber

Hello everyone, I'm currently working on a little project that has been puzzling me for some time. If you send a laser beam into a fiber, the ingoing angle is sometimes slightly different than the outgoing angle. To measure this ratio of angles, I am currently using a setup that looks like...
37. ### Angle of incidence, angle of refraction and angle of reflection

Homework Statement A light ray strikes the surface between two transparent materials as shown. Each angle is labeled with a letter. Give the letters for the angle of incidence, angle of refraction and angle of reflection, in that order Homework Equations...
38. ### Angle of Incidence with partial reflection and partial refraction

Homework Statement A beam of light in air strikes a piece of glass (n=1.51) and is partially reflected and partially refracted. Find the angle of incidence if the angle of reflection is twice the angle of refraction. Homework Equations n1sintheta1 = n2sintheta2 The Attempt at a...
39. ### Size of the angle of incidence?

If the angle between an incident ray and a reflecting surface is 23°, what is the size of the angle of incidence? Im not quite sure what the formula for this would be, I can't find it in my book :| any help would be very much appreciated. Thank you
40. ### Why Does the Calculator Show an Error When Solving for the Angle of Incidence?

b]1. A light beam coming from an underwater spotlight exits the water at an angle of 68° to the vertical. At what angle of incidence did it hit the air-water interface from below the surface? [b]2. snell's law n1sin\Theta1=n2sin\Theta2 [b]3. sin\Theta1=1.33(sin68) After doing this...
41. ### Snell's law, critical angle, and angle of incidence

Homework Statement A pair of students measure the refraction of light in passing from acetone into air for several angles. When the angle of incidence is 30, the angle of refraction is 42. b) What is the angle of incidence (in degrees) when the refracted angle is the critical angle? Homework...
42. ### Can the angle of refraction be equal to the angle of incidence?

Snell's law says n1sin(theta1) = n2sin(theta2) The angle of refraction theta2 can be greater or less than the angle of incidence theta1. That's fairly obvious. My question is if theta2 = theta1 then we don't have an interface (because n1 = n2) so the light is still in the same medium, and...
43. ### Angle of Incidence and Reflection.

Hi, Can someone please eloborate me why the Angle of Reflection is always same as the Angle of Incidence. I want the explanation at photon and molecular interaction level. Thanks in advance. - Pavan.
44. ### Angle of incidence, reflection, and refraction

Homework Statement What are the difference among angle of incidence, reflection, and refraction when light strikes two parallel surfaces? What does it mean "light is incident on film"?-is that the angle of incidence? The Attempt at a Solution I know how to find all of...
45. ### Transimission Of EM waves in conductors at an angle of incidence

We know that in electrodynamic when an incident Electromagnetic wave strikes a charged barrier it can either be reflected or transmits. And both of the incident, reflected and transmitted waves are in the same plane called plane of incidence. Now, i met a problem in which they state that the...
46. ### At what angle of incidence is amplitude coefficient of reflection parallel to the inc

At what angle of incidence is amplitude coefficient of reflection parallel to the incidence plane 0? my solution is that by Fresnell's equation, r//=tan(i-i)/tan(i+i)=0, i=i`,i=90.so for whatever surface,angle of incidence should be 90. is it correct? different from the answer!
47. ### Maximum Angle of Incidence for Glass-Water Boundary?

Homework Statement A 1.0-cm-thick layer of water stands on a horizontal slab of glass. Light from a source within the glass is incident on the glass-water boundary. What is the maximum angle of incidence for which the light ray can emerge into the air above the water? Homework Equations...
48. ### What Angle of Incidence Causes Total Reflection of X-rays in Calcite?

Problem: The index of refraction for x-rays of wavelength 0.708A incident on calcite is 1-1.85E-6. What angle of incidence will give total reflection of such X rays? Using Bagg's Law: n(lambda)=2asin(theta), I get and angle of -45.07 degrees. Is this all that is required of the...
49. ### Angle of Incidence - Find Reflection & Refraction Angles

a beam of light in air strikes a piece of glass (n=1.56) and is partially reflected and partially refracted. find the angle of incidence if the angle of reflection is twice the angle of refraction.
50. ### Angle of Incidence for Internal Reflection

Homework Statement In the figure shown below, a light ray enters a glass slab (with index of refraction nglass = 1.65 ) at point A and then undergoes total internal reflection at point B. The medium that surrounds the glass slab is a liquid whose index of refraction, nliquid =...