Question
Which of the following statements with regard to stealth technology is/are correct?
1Stealth objects have a very small radar cross-section and are coated with Radar Absorbing Material.
2Stealth objects can be detected using specific frequencies.
3Stealth objects are coated with metamaterials to increase the scattering of electromagnetic radiation.
A1 only
B2 and 3 only
C1 and 2 only
D1, 2 and 3
Each Statement — Verified Against Stealth Technology Science
1
“Stealth objects have a very small radar cross-section and are coated with Radar Absorbing Material” — TRUE
This is the foundational description of stealth technology — confirmed across all defence and scientific sources:
Small radar cross-section + Radar Absorbing Material (RAM)
✓ Correct — foundational stealth principle
Radar Cross-Section (RCS): RCS measures how detectable an object is by radar. A conventional aircraft may have an RCS of ~10 m² or more. A stealth aircraft like the F-22 Raptor has an RCS estimated at ~0.0001 m² — like a marble on radar. The entire design philosophy of stealth is to minimise RCS through:
• Special angled shapes that deflect radar energy away from the receiving antenna
• Curved surfaces that scatter rather than retro-reflect radar
• Embedded weapons/engines to remove protruding features
Radar Absorbing Material (RAM): RAM coatings absorb radar energy (convert it to heat) rather than reflecting it back. Iron ball paint, carbon-fiber composites, and ferrite-based coatings are common RAMs used on stealth aircraft (F-117, B-2, F-22, Su-57, AMCA).
✓ Foundational stealth principle
Small RCS + RAM coating = two pillars of stealth. F-22 RCS ≈ marble; B-2 RCS ≈ golf ball. RAM absorbs radar energy as heat.
2
“Stealth objects can be detected using specific frequencies” — TRUE
Stealth technology is optimised to defeat radar at specific frequency bands (typically X-band and Ku-band used by most military fire-control radars). However, at different frequencies, stealth becomes much less effective:
Stealth objects CAN be detected using specific frequencies
✓ Correct — VHF/VLF radars defeat stealth
VHF (Very High Frequency) and UHF radars: Long-wavelength radars (metre-wave radars) can detect stealth aircraft because the aircraft’s dimensions approach the radar wavelength, causing resonance effects that increase the effective RCS. The Russian Nebo SVU and Protivnik-GE radars operate in VHF specifically to detect stealth.
Bistatic radar: Using transmitters and receivers in different locations (not co-located) — stealth shapes designed to deflect energy away from the transmitter still reflect energy toward a receiver elsewhere.
Infrared/thermal detection: Even “radar-invisible” stealth aircraft have heat signatures from engines — infrared search and track (IRST) systems can detect them.
Statement 2 is a well-established fact in electronic warfare.
✓ VHF/UHF radars and bistatic systems defeat stealth
X-band stealth ≠ VHF stealth. Long-wavelength radars (VHF/UHF), bistatic radar, and IRST can detect stealth objects. Stealth is frequency-specific, not absolute.
3
“Stealth objects are coated with metamaterials to increase the scattering of electromagnetic radiation” — FALSE — the word “increase” makes it wrong
Statement 3 is wrong on the direction of effect. Metamaterials are used in stealth to REDUCE (not increase) electromagnetic scattering:
“Metamaterials to INCREASE scattering of electromagnetic radiation”
✗ Exact opposite — metamaterials REDUCE scattering
What metamaterials actually do in stealth:
• RCS reduction — metamaterials are engineered to absorb or redirect radar waves, drastically reducing how much is reflected back to the radar receiver
• Electromagnetic cloaking — some metamaterial configurations can bend electromagnetic waves around an object, making it effectively “invisible”
• Negative refractive index — metamaterials can have negative permittivity and permeability, producing exotic wave-bending properties
The scientific sources confirm: metamaterials are used for “radar cross-section (RCS) reduction, electromagnetic camouflage, and thermal signature management” — all aimed at REDUCING detection, not increasing scattering.
Statement 3 reverses the engineering purpose of metamaterials in stealth — increasing scattering would make an object MORE detectable, which defeats the entire purpose.
✗ Metamaterials REDUCE scattering — not increase it
Metamaterials = RCS reduction, electromagnetic cloaking, wave absorption. Statement 3 says “increase scattering” = exact opposite. More scattering = more detectable.
Stealth Technology — Key Facts for UPSC
| Parameter | Detail |
| Radar Cross-Section | Measure of radar detectability · Stealth aircraft: 0.0001–0.01 m² · Conventional aircraft: 1–100+ m² |
| Radar Absorbing Material | Absorbs radar energy as heat · Iron ball paint · Carbon fiber composites · Ferrite coatings · Applied to all stealth platforms |
| Stealth shape design | Angled surfaces that deflect radar away from receiver · Elimination of protruding surfaces · Embedded engines/weapons · Curved surfaces |
| Detection frequencies | VHF/UHF (metre-wave) radars effective against stealth · Russian Nebo SVU, Protivnik-GE · Bistatic radar · IRST (infrared) · Statement 2 ✓ |
| Metamaterials in stealth | Used to REDUCE scattering (RCS reduction) — NOT increase. Negative refractive index. Electromagnetic cloaking. Wave absorption. Statement 3 reverses this. |
| Stealth aircraft (examples) | F-117 Nighthawk (retired) · B-2 Spirit · F-22 Raptor · F-35 Lightning II · Su-57 (Russia) · J-20 (China) · India’s AMCA (in development) |
| India AMCA | Advanced Medium Combat Aircraft · India’s indigenous 5th-gen stealth fighter · Being developed by ADA/HAL · Incorporates RAM coatings and stealth shaping |
| Statement 3 error | The word “increase” makes Statement 3 wrong. Stealth uses metamaterials to DECREASE/ABSORB electromagnetic scattering. Increased scattering = increased radar visibility = defeated stealth purpose. |
Memory Trick
🧠 Remember It This Way
Statement 3 trap — “increase” is the lie: Stealth’s entire purpose is to be less detectable. Anything that INCREASES electromagnetic scattering increases detectability — the opposite of stealth. Metamaterials reduce RCS. The single word “increase” makes Statement 3 false.
Statement 2 is subtle but true — “specific frequencies”: Stealth is optimised for the frequencies used by fire-control radars (X-band). VHF/UHF long-wavelength radars are much more effective against stealth. India’s DRDO has been developing such radars for this reason.
RAM = absorb, not reflect: RAM converts radar energy to heat. Regular metal reflects radar — that’s why you can see aircraft. RAM-coated surfaces absorb radar. Metamaterials take this further — they can even bend waves around the object.
