Common JEE Mistakes

Common JEE Mistakes

### Mistake 1

Confusing interference and diffraction conditions.

### Correct Relations

Interference:

$$\Delta x=n\lambda$$

Diffraction:

$$a\sin\theta=n\lambda$$

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### Mistake 2

Using Malus law without angle between axes.

### Correct Relation

$$I=I_0\cos^2\theta$$

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### Mistake 3

Forgetting phase change in thin film.

### Correct Approach

Consider phase reversal at reflection.

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### Mistake 4

Confusing fringe width with fringe position.

### Correct Relations

Fringe width:

$$\beta=\frac{\lambda D}{d}$$

Fringe position:

$$y_n=n\frac{\lambda D}{d}$$