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Lesson Posted on 06 Mar Schools/CBSE Schools CBSE/Class 9/Science Tuition/BSc Tuition/Mathematical Physics
Reflection Of Light (Questions)
Soumi Roy
I am an experienced, qualified tutor with over 5 years of experience in teaching maths and physics across...
Reflection of Light Rays on a Reflecting Surface:
When a light ray strikes a surface separating two media with different optical properties, part of the light energy is reflected back to the media where it coming from. When light strikes a perfectly reflecting surface, such a mirror for example, all the light energy is reflected.
We first look at the vocabulary used to describe the reflection of light.
The surface separating the two media is called the interface or boundary.
The point at which the incident ray strikes the interface is called the point of incidence.
i is the angle made by the incident ray and the normal to the interface and is called the angle of incidence.
r is the angle made by the reflected ray and the normal to the interface and is called the angle of reflection.
Laws of reflection:
(1) The incident light ray, the reflected light ray and the normal to the interface at the point of incidence make a plane called the plane of incidence
(2) The angle of incidence and the angle of reflection have the same size.
Example 1: A light ray strikes a reflective plane surface at an angle of 56° with the surface.
a) Find the angle of incidence.
b) Find the angle of reflection.
c) Find the angle made by the reflected ray and the surface.
d) Find the angle made by the incident and reflected rays.
Example 2: A ray of light is reflected by two parallel mirrors (1) and (2) at points A and B. The ray makes an angle of 25° with the axis of the two mirrors.
a) What is the angle of reflection at the point of incidence A?
b) What is the angle of reflection at the point of incidence B?
c) If the distance between the two mirrors id d = 4 cm and the length L of the two mirror system is 3 meters, approximately how many reflections take place between the two mirrors?
d) In a real system, at each reflection, there are losses of the light energy travelling between the two mirrors. If L and d are fixed, what can be done to decrease the number of reflections on the mirrors and hence the energy lost by reflection?
Solution:
a) i = 90 - 25 = 75 °
b) the two mirrors are parallel and AB intersect both of them, hence angle r and i' are alternate interior and therefore equal in size. Also r = i (law of reflection). Hence i' = r = i = 75 °
c) If the distance between the two mirrors id d = 4 cm, AC can be calculated as follows
tan(75°) = AC / d = AC / 4
AC = 4 tan(75°) = 15 cm
The number of reflections N that will take place between the two mirrors may be approximated as follows.
N = L / AC = 3 m / 15 cm = 20
d) Let the angle made by the light ray and the axis of the two mirror system be ? instead of 25 °.
The angle of incidence i = 90 - ? = r = i'
tan(i') = tan( 90 - ?) = cot (?) = AC / d
AC = d cot(?)
number of reflections = N = L / AC = L / d cot(?)
If L and d are fixed, the only way to decrease N is to increase cot(?) and hence decrease ?.
Lesson Posted on 11 Jan CBSE/Class 11 CBSE/Class 12 Schools/CBSE Schools
Amar Singh
I have good experience.
1. ( sinA )2 + (cosA)2 = 1
2. (tanA)2 + (cotA)2 = 1
3. SinA = 1 /cosecA
4. CosA = 1 /secA
5. TanA = 1/cotA (also inverse as secA= 1/ CosA)
6. sin2a = 2 sinA CosA
7. cos2a = (cosa)2 - (sina)2
= 2(cosa)2 - 1
= 1 - 2 (sina)2
8. tan2a = 2tana / 1- (Tana)2.
read lessLesson Posted on 20/11/2017 Schools/CBSE Schools
How to Study Maths: 7 Tips for Solving Maths Problems
Rupam Sasmal
I am an experienced, qualified teacher and tutor with over 10 years of experience in teaching Maths,...
Maths is one of those subjects which you can easily spend hours studying but end up none the wiser. However much you have studied, if you can not solve the problem on day of the test, you are lost. Thankfully, there are some techniques for studying maths that you can do regardless of your level.
7 Tips for Maths Problem Solving:
It is impossible to study maths properly by just reading and listening. To study maths you have to roll up your sleeves and actually solve some problems. The more you practice answering maths problems, the better. Each problem has its own characteristics and it’s important to have solved it in numerous ways before tackling the exam. There is no escaping this reality, to do well in a Maths exam you need to have solved a LOT of mathematical problems beforehand.
When you’re practising with these problems, it’s important to work through the process for each solution. If you have made any mistakes, you should review them and understand where your problem-solving skills let you down. Understanding how you approached the problem and where you went wrong is a great way of becoming stronger and avoiding the same mistakes in the future.
3. Master the Key Concepts:
Do not try to memorise the processes. This is counter-productive. It is much better and rewarding in the long-run to focus on understanding the process and logic that is involved. This will help you understand how you should approach such problems in the future.
Remember that Maths is a sequential subject so it’s important to have a firm understanding of the key concepts that underpin a mathematical topic before moving on to work on other, more complex solutions which are based on understanding the basics.
Sometimes you can get stuck trying to solve part of a maths problem and find it difficult to move on to the next stage. It’s common for many students to skip this question and continue on to the next. You should avoid doing this and instead spend time trying to understand the process of solving the problem. Once you have grasped an understanding of the initial problem, you can use this as a stepping stone to progress to the remainder of the question.
5. Create a Distraction Free Study Environment:
Mathematics is a subject that requires more concentration than any other. A proper study environment and a distraction free area could be the determining factor when solving complex equations or problems in geometry, algebra or trigonometry!
Studying with music can help create a relaxing atmosphere and stimulate the flow of information. Having suitable background music can foster an environment of maximum concentration. Of course, you should steer clear of Pitbull and Eminem, instrumental music is the best thing in these times.
Mathematics has specific terminology with a lot of vocabulary. We suggest you create Notes or Flashcards with all the concepts, terminology and definitions you need to know. You should include their meanings, some key points and even some sample answers so you can consult them at any time and recap.
As much as possible, try to apply real-world problems when approaching maths. Maths can be very abstract sometimes so looking for a practical application can help change your perspective and assimilate ideas differently.
Probability, for example, can be used in everyday life to predict the outcome of something happening and determine whether you want to take a risk such as if you should buy a lottery ticket or gamble.
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Lesson Posted on 19/09/2017 Schools/CBSE Schools
BlueJ Program For CBSC/ICSE Student
Bishal Saha
I was both student and teacher of computer for a long time.
Consecutive numbers program using array:
class Consecutive
{
public static void main(String[] args)
{
int a[]={52,10,85,14,32,78,15,11,53,86};
int p=a.length;
System.out.println("====Consecutive Numbers Are:====");
for(int i=0;i<p;i++)
{
for(int j=i+1;j<p;j++)
{
if((a[i]+1)==a[j])
{
System.out.println(a[i]+","+a[j]);
}
else{
if(a[i]==a[j]+1)
{
System.out.println(a[j]+","+a[i]);
}
}
}
}
}
}
Lesson Posted on 19/09/2017 Schools/CBSE Schools
Bishal Saha
I was both student and teacher of computer for a long time.
Output:
15 14 13 12 11
10 9 8 7
6 5 4
3 2
1
public class Q19c
{
public static void main(String args[])
{
int b=5,c=5;
for(int i=15; i>=1; i--)
{
System.out.print(i+"\t");
if((16-i)==b)
{
System.out.println();
c--;
b=b+c;
}
}
}
}
Lesson Posted on 05/09/2017 Schools/CBSE Schools
6 Tips To Write The Perfect Answer In Cbse Board Exams
Edusmart Skills
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Asked on 25/08/2017 Schools/CBSE Schools
Lesson Posted on 09/08/2017 Schools/CBSE Schools
How To Understand Propositions Better? (For Primary School Students )
BilvaaGuru Learning
Bilvaa Guru Learning is an organization dedicated to making students learn, - covering various areas,...
Asked on 31/07/2017 Schools/CBSE Schools
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Lesson Posted on 18/07/2017 CBSE/Class 4/English/Grammar CBSE/Class 8 CBSE
M.mallick
I graduated from Calcutta University , Dept of Law (hazra campus). I am rewarded with Atul Binod Akhyoy...
Exercise on Modals: (Class 8)
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