Interference Pattern with Red and Green Light

❓ Question

In a Young’s double slit experiment, the source is white light.

One of the slits is covered by a red filter and another by a green filter.

In this case:

1. there shall be an interference pattern for red distinct from that for green.
2. there shall be no interference fringes and central fringe is given and outer edges is red.
3. there shall be no interference fringes.
4. there shall be alternate interference fringes of red and green.

Choose the correct option.

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🖼 Question Image

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✍️ Short Explanation

This problem is based on:

👉 Young’s Double Slit Experiment
👉 Coherent sources
👉 Interference of light.

Main idea:

Interference occurs only when waves have:

$$\text{same frequency and constant phase difference}$$

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🔷 Step 1 — Condition for Interference 💯

For sustained interference:

$$\text{Sources must be coherent}$$

That means:

✔ Same wavelength/frequency
✔ Constant phase difference

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🔷 Step 2 — Analyze the Given Situation

One slit has:

$$\text{Red light}$$

Other slit has:

$$\text{Green light}$$

Since:

$$\lambda_{red}\neq\lambda_{green}$$

their frequencies are different.

Hence the two waves are not coherent.

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🔷 Step 3 — Result on Screen

Because the two lights have different frequencies:

$$\text{No sustained interference pattern forms}$$

Therefore:

$$\boxed{\text{No interference fringes are observed}}$$

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🔷 Step 4 — About Central Region

At center:

Both colors overlap.

So the central region may appear mixed in color, but no stable bright-dark fringe pattern forms.

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🔷 Step 5 — Correct Option

$$\boxed{3}$$

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🔷 Step 6 — JEE Trap Alert 🚨

❌ Different colors ke separate fringes assume kar lena

❌ White light YDSE concept directly apply kar dena

❌ Coherence condition ignore kar dena

Remember:

$$\boxed{ \text{Different frequencies } \Rightarrow \text{No sustained interference} }$$

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✅ Final Answer

$$\boxed{3}$$

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📚 Related Topics

• Lens Formula in Different Medium
• Resultant Amplitude and Phase of Two Waves
• Interference of Light Waves Using Phase Difference