Q: When light goes from air into a denser medium like glass, its wavelength generally?
Answer: Decreases
Explanation: Light slows down in a denser optical medium. Frequency stays the same at the boundary. Since λ = v/f, wavelength decreases when speed decreases.
Q: X-rays are commonly produced when?
Answer: High-speed electrons are suddenly decelerated at a metal target
Explanation: X-rays can be produced by rapid deceleration of electrons at a target. This process is called bremsstrahlung in many texts. X-rays can also arise from inner-shell electron transitions.
Q: Which statement about gamma rays is generally correct?
Answer: They are highly energetic and strongly penetrating
Explanation: Gamma rays are very high frequency EM waves with high photon energy. Their high energy makes them strongly penetrating and ionizing. Dense materials like lead are often used for shielding.
Q: Many substances glow under ultraviolet light because UV can cause?
Answer: Fluorescence
Explanation: Ultraviolet light can excite electrons in some materials. When electrons fall back, they emit visible light, producing fluorescence. Security markings often use this effect.
Q: Which EM waves are primarily used for AM/FM broadcasting over large areas?
Answer: Radio waves
Explanation: Radio waves are used for AM and FM broadcasting. Their long wavelengths allow efficient transmission and reception with antennas. Different bands are allocated for different services.
Q: Polarizing sunglasses reduce glare mainly because reflected light from horizontal surfaces is often?
Answer: Partially horizontally polarized
Explanation: Reflected light from roads or water is often partially polarized horizontally. Polarizing sunglasses block much of that horizontal component. This reduces glare and improves visual comfort.
Q: The effective length of a half-wave dipole antenna is approximately?
Answer: λ/2
Explanation: A half-wave dipole antenna has length about λ/2. This length supports resonance at the operating frequency. A quarter-wave monopole is about λ/4 above a ground plane.
Q: The energy of a photon of wavelength 500 nm is closest to?
Answer: 4.0 × 10^-19 J
Explanation: Use E = hc/λ with h ≈ 6.63 × 10^-34 J·s and c ≈ 3.0 × 10^8 m/s. For λ = 5.0 × 10^-7 m, E ≈ 4.0 × 10^-19 J. Shorter wavelength photons carry more energy.
Q: Electromagnetic radiation with typical wavelength around 10^-10 m is generally classified as?
Answer: X-rays
Explanation: Wavelengths around 10^-10 m fall in the X-ray region. X-rays have much shorter wavelengths than ultraviolet. Their high energy allows them to penetrate soft tissues to some extent.
Q: Which electromagnetic wave has the shortest wavelength?
Answer: Gamma rays
Explanation: Gamma rays have the shortest wavelength and highest frequency in the electromagnetic spectrum. They are produced during nuclear reactions and radioactive decay. Their wavelengths are less than 10 picometers.