Learn IIT Foundation Classes with Free Lessons & Tips

One of the areas of physics in which measurement has been bewildering is astronomy. How far away are the stars? How large is the universe? 

These are the most fundamental and profound questions. One can trace the evolution of astronomy through the changing techniques of calculating stellar distances. Untill the end of nineteenth century, the only way astronomers could make these calculations was by measuring parallax. 

You are familiar with the phenomenon of parallax without even realizing it. Wherever you are sitting, look around and find a stretch of wall with some sort of feature along it- a doorway or a picture hanging on it. Now stretch your hand straight out in front of you and raise a finger so that it is to one side or the other side of the feature. Now first close your right eye and then close your left eye. You will see that your finger jumped from left to right relative to the feature. If you move your finger closer the movement will be more. This effect is parallax. It happens because of the switch to different line of sight in observing an object. 

Be in touch to know how this phenomenon is used to calculate astronomical distances. 

As we know, JEE is the toughest entrance test in India. But how many of you know the tricks to mark correct answers for MCQs in JEE Main and JEE Advanced? I know a few.

In JEE, all questions are objective. The Multiple Choice Questions (MCQs) has four answers, out of which sometimes only one and at times two options are correct. Students need to circle the correct option for every question and earn marks.

It is usually seen that candidates consider objective questions easy as compared to subjective. Despite of the wide spread liking towards MCQs and IIT JEE paper pattern, multiple choice questions could be difficult to tackle. At times, the choices may appear similar and therefore you might get confused. In order to answer the questions correctly, students need to have deeper insight of every topic in the syllabus. Students can use the below mentioned tricks for both online and offline exams:

Be Calm Candidates should make sure they are stress free and calm before writing IIT JEE test. Since, due to tension you may lose concentration and might mark a wrong answer. Understand the question Identify the important part of the question and apply your logic. Understand what the question is before marking the answer. Tick the answer only when you are sure. Choosing correct answer is really important, since every wrong answer might result in deduction of marks (due to negative marking in the exam).

Example: From a tower of height H, a particle is thrown vertically upwards with a speed u, then the time taken by the particle to hit the ground, is ‘n’ times taken by it to reach the highest point of its path.                                                                                                                          (IIT-JEE Mains 2014)

(a)  2gH=n²u²                                                     (b) gH = (n-2)²u²

(c)  2gH =nu²(n-2)                                   (d) gH = (n-2)u²

Immediately, identity the topic and apply concept related to it (Projectile motion in this case). Make the diagrams for better understanding to make sure you land up to the right answer choice.

Check the Dimensions This technique is very handy in Physics paper, where we can filter options by looking at their dimension. Let’s say, we are to find the speed, then we can safely filter out options whose dimension does not equals m/sec. Believe me, it will save a lot of your time.

Example: A highly rigid cubical block A of small mass M and side L is fixed rigidly onto another cubical block B of the same dimensions and of low modulus of rigidity ɳ such that the lower face of A completely covers the upper face of B. The lower face of B is rigidly held on a horizontal surface. A small force F is applied perpendicular to one of the side faces of A. After the force is withdrawn, block A executes a small oscillation. The time period of oscillation is: (IIT JEE 1992)

(a)2π MɳL                              (b) 2π Mɳ/L

(c) 2π ML/ɳ                            (d) 2π M/ɳL

Sol: Dimensional formula of ɳ = [MLT^-2]/ [L] [L] = [ML^-1 T^-2]

Now check for the dimension of Time period in each option. Let us take the first option. The final dimensional formula of that answer comes to be [MT^-1].

Option (b) comes out to be [ML^-1 T^-1]

Option (c) comes out to be [LT]

Now check option (d). It’s [M]/ [ɳ] [L]

= [M]/ [ML^-1 T^-2] [L] = [T]

Don’t be in hurry during JEE Giving the right answer is very crucial in IIT JEE therefore mark the answer carefully. Don’t guess the answer too soon! Take some time to think and make necessary calculations. Stop and read the question and options carefully.

Method of Assumption This is another important method. In some of the questions, some unknown quantities will be given. Here, we assign some values to these quantities without changing the conditions given. This is almost similar to the method of substitution.

Example: If a(n) denotes the nth term in an Arithmetic Progression. Then

1/a(1)a(2) +1/a(2)a(3) +………………………………+1/a(n-1)a(n)=

(a) n-1/a (1) a (n)                               (b) n/a(1)a(n+1)

(c)n-2/a(1)a(n-1)                               (d) n/a(1)a(n)

Sol: Take a simple AP=1, 2, 3, 4…..let us take n=3.

Therefore our questions comes to be:1/1*2 +1/2*3 =4/6 =2/3= n-1/a(1)a(n).

Hence the correct option is (a).

Choose technically correct option and Generalize Questions It is often seen that people tend to ignore options like ‘all of the above’ and ‘none of the above’ thinking such options are never correct. In reality, these options tend to be right more often.  Also, don’t jump into any option abruptly.

Questions like ax+by+cz= k, can we solved by using general values like a=1, b=1, c=1 to see if it solves our purpose.

Do a little guess work Even though guess work is not always the best practice, it might work at times. If you are not sure of an answer, make a guess! Delete some options which you think are in correct and try to relate the leftovers with the questions to check what answer you get. Remember, guess work is not always beneficial. So try to avoid it! 

Example: When a rubber-band is stretched by a distance x, it exerts a restoring force of magnitude F = ax + bx² where a and b are constants. The work done in stretching the unstretched rubber-band by L is:

(a)  aL² + bL³                                        (b) (aL² + bL³) / 2

(c)  aL² / 2 +  bL³ / 3                    (d) aL² / 4 +  bL³ / 6

As we can observe from the question that a and b are with different powers of x and hence there the answer is most unlikely to have same coefficients. Hence options a and b can be eliminated and even with a little amount of knowledge, we can chose among c and d.

Don’t change your answer Avoid changing your answers frequently. Generally, first answer is always correct. Regularly changing the answer might prove wrong at the end. This also leads to confusion. Therefore, stick to one answer regularly.

Reverse engineering Reverse engineering, taking step backward. Instead of solving complete equation, we just apply value in the equation to see if it solves it.

Example: The straight line (2+α)X + (1+ α)Y=5+ α , for different values of α passes through the fixed point

(a) (2,9)                                  (b) (2, -9)

(c ) (-2,-9)                               (d ) (-2, -9)

Move on Despite of so many attempts, if you are not getting the right answer, switch to the next question. Sticking to just one question will waste your time. Solve other questions and return to this one once you have done all the rest. You can spend the remaining few minutes in solving this question. Later on once you have done filtering, dimension check, you can apply law of probability (as per option 1) and choose one option. Remember, probability is now on your side.

Discard highest and lowest outliers Outliers mean choices having extreme values. If your test paper has any question which have answers in numerical values, discard the extremes. In 60% cases, the highest and lowest values are not right. So, be very careful while choosing the answer. They have high probability of being wrong. So candidates can safely stay away from this unfamiliar zone.

Example: Let A, B, C be three sets of complex number as defined below

A = {z: Imz ≥ 1} , B={z:|z – 2 – i| = 3} , C = {z: Re ((I – j) z) = }. The number of element in the set A ∩ B ∩ C is

(a) 0                                 (b) 1

(c)  2                                (d) ∞

Here the answer is 1. This is not generalized rule but again applicable at many places.

Choose one among the two options If you have already checked out two incorrect answers, choose one out of the remaining options. You can use the first point to select the correct answer. 

Attempt the ‘no-negative marking’ questions At times, there are questions like ‘match the following’ in the IIT JEE test. These questions don’t carry negative marking therefore you are free to take chance. You should never leave such questions un-attempted. You should read and know the marking scheme correctly to attempt every question and earn marks. Usually exams marking pattern is +4 for each correct answers and -1 for each negative. And, assuming all options have an equal probability of being correct, student can at the leave have a minimum score of 0.25*n out of n questions (0.25 n *4 – 0.75n*1) by choosing only 1 option. In case, there is no negative marking, you can score 1*n. Hence, never leave any question unanswered if there is no negative marking.

If we go via topics, we can summarize the following:

Memorize easiest topics to get good marks

1)  Algebra can be made easier if you have the ability to picture functions as graphs and are good at applying vertical and horizontal origin shifts carefully as zeroes of functions and other specific values can be done in much less time using these techniques.

2)  Differential calculus again relates well to roots of equations, especially if you use the Rolle’s and Lagrange’s theorems.

3)  Complex numbers is very important chapter for JEE. It can be used to solve questions in co-ordinate geometry too. Trigonometric questions require applications of De Moivre’s theorem.  Every year, two to three problems (of purely complex number) are asked. Hence mastering complex numbers, vectors, 3-D and Definite integral must be on top priority.

4)  Permutation-Combination and Probability is another very important topic in algebra. You need to be thorough with the basics of Bayes’ theorem, derangements and various ways of distribution, taking care of cases where objects are identical and when they are not.

5)  Matrices can be related to equations, hence a 3×3 matrix can actually be visualised as being three-planed in 3D geometry. Determinants have some very nice properties, for instance, the ability to break them into two using a common summand from a row/ column, which should be made use of in tougher questions.

6)  Integral calculus can be simplified using tricks and keeping in mind some basic varieties of integrable functions. Remembering the properties and applying them wisely saves lot of time.

7)  Coordinate geometry requires a good working knowledge of the parametric forms of various conic sections and an ability to convert the other, tougher ones to these basic forms and then interpret the solutions accordingly.

Finally the only one way to do well in Mathematics is to practice problems keeping in mind the pattern of questions in the previous years’ JEE papers. Conceptual clarity, application skills and awareness to the prescribed syllabus should be the main focus. Practice the most relevant numerical daily to develop speed. Pay special attention to the topics like Mole concept, Chemical Equilibrium and Electrochemistry.

8)  Take a careful and patient approach for Organic Chemistry giving particular attention to the topics like Stereochemistry, GOC (General Organic Chemistry) and Functional Group Analysis.

9)  In Inorganic chemistry, most of the questions which are asked are really conceptual, concerned with structures, processes and applications and are very direct.

10)  Special attention is a must for the topics like Chemical Bonding and Coordination Chemistry.

11)  Mechanics is one topic in Physics that is considered less scoring by most experts. However to add to the dilemma, this is also the topic that forms the major portion of the JEE (Advanced) in terms of marks. So this topic cannot be neglected.

12)  Modern Physics with its atoms, nuclei and radiations are some of the topics, which cannot be ignored during IIT JEE Test. In fact, these topics will help you earn about 20-25 marks in the exam. Also, it requires not more than a couple of days to understand this topic. So, memorize easiest topics to score well in the test.

13)  Kinematics and Particle dynamics are very important topics of Mechanics that make regular appearance in the JEE papers.

14)  Thermodynamics is important from the terms of both Physics and Chemistry so concentrate on that as well.

15)  One must also try to concentrate on other scoring topics to ensure a better performance, for example Optics, Electricity and Magnetism, etc.

Note: It is wise to cover Wave Optics first in ‘Optics’ topic. The reason is that the portion is smaller compared to Ray Optics and thus, quick to cover.

OTHER KEY GENERAL POINTS

• Stay focused and maintain a positive attitude.
• Develop speed. Refer to reputed mock-test series to build a winning exam temperament. Solve the past year’s IIT-JEE papers. Focus on your weak areas and improve upon your concepts.
• Practice of JEE level questions is necessary as it improves your reasoning and analytical ability.
• Remember it is quality of t read less