A sound wave has wavelength 1.7 m and speed 340 m/s. Its frequency is MCQ with Answer and Explanation

Explanation:
EM waves transverse: E ⊥ B ⊥ propagation direction. Derived from Maxwell's equations. Memory tip: 'EM wave: right-hand rule for E×B direction'. Wave property frequently tested in competitive modern physics sections.

Explanation:
Covering part of a lens reduces the amount of light reaching the image, making it fainter, but the entire image is still formed because light from each object point can pass through the uncovered portion and converge to the corresponding image point. Image position, size, and nature remain unchanged. Memory aid: 'Partial lens coverage ⇒ reduced intensity, not partial image'. This conceptual question tests understanding of image formation principles, commonly featured in competitive exams to identify misconceptions about ray optics. Always recall that every point on lens contributes to entire image.

Explanation:
When light travels from an optically denser medium to a rarer medium, it bends away from the normal. As the angle of incidence increases, the angle of refraction also increases. The specific angle of incidence for which the refracted ray grazes the surface (meaning the angle of refraction is exactly 90 degrees) is defined as the critical angle.