💡 Explanation (Answer: C)

A light ray traveling along the normal to the surface enters the medium without changing its spatial direction or undergoing deviation. However, because the refractive index of the lens material is greater than air, the velocity of the light must decrease.

💡 Explanation (Answer: D)

A cylindrical lens has no refractive power along its axis meridian because the curvature in this direction is completely flat. Consequently, the maximum refracting power is located exactly \(90^\circ\) perpendicular to the cylinder axis.

💡 Explanation (Answer: C)

Refraction causes light rays coming from the submerged portion of the stick to bend away from the normal as they exit the water into the air. This abrupt change in direction alters the perceived origin of the light, making the stick appear bent at the surface interface.

💡 Explanation (Answer: C)

The human visual system is sensitive only to a narrow band of electromagnetic radiation known as the visible spectrum. This range extends approximately from 400 nanometers for violet light to 700 nanometers for deep red light.

💡 Explanation (Answer: B)

Dispersion occurs because different wavelengths of light experience slightly different refractive indices and travel at different speeds through a medium. When white light passes through a prism, these varying angles of refraction cause the light to separate into its constituent spectral colors.

💡 Explanation (Answer: B)

To perceive a rainbow, the observer must face the falling rain while the sun is positioned directly behind them. This specific geometry is required so that light entering the water droplets can undergo internal reflection and emerge back toward the observer’s eyes.

💡 Explanation (Answer: A)

In this selection of the electromagnetic spectrum, infrared waves occupy the region with the longest wavelengths and lowest frequencies. In contrast, ionizing radiations such as X-rays and gamma rays have much shorter wavelengths and higher energy levels.

💡 Explanation (Answer: A)

Projectors require a convex lens to act as a magnifying system for the slide or display panel. This converging lens projects a highly enlarged, real, and inverted image onto a distant screen.

💡 Explanation (Answer: B)

A rainbow is naturally a complete circle centered on the antisolar point opposite the sun. Observers on the ground only see a semi-circular arc because the horizon blocks the lower half of the circular pattern.

💡 Explanation (Answer: B)

Mass density represents mass per unit volume, whereas optical density is a measure of a medium’s ability to slow down light. Turpentine is a classic example because it floats on water due to a lower mass density, but its higher refractive index means it has a greater optical density.