Everyday Science

The film in a camera functions similarly to the retina in the human eye because both capture the image formed by the lens. The retina detects light and converts it into signals for the brain, just as film records the image in a camera.

Detergents reduce the surface tension of water, allowing it to spread and penetrate fabrics more effectively, which helps in loosening and removing dirt from clothes.

The rear view mirror of a motor vehicle is convex because it allows the driver to see a wider field of view behind the vehicle, enhancing safety by reducing blind spots.

When moving from bright light to a dark room, the pupil needs to dilate to allow more light in. The iris controls pupil size, and it cannot dilate immediately, causing temporary difficulty in seeing clearly.

Fats provide the highest calorific value among the given options, yielding about 9 kcal per gram, whereas carbohydrates and proteins provide about 4 kcal per gram, and vitamins do not provide energy.

A lactometer is a specialized hydrometer designed specifically to measure the specific gravity of milk, which helps determine its purity and quality.

Quartz crystals in watches operate based on the piezo-electric effect, where mechanical stress on the crystal generates an electric charge, allowing precise timekeeping.

The primary colors used in color television are red, green, and blue. These colors are combined in various ways to produce the full spectrum of colors seen on the screen.

Television signals are electrical signals that carry audio and video information. To display the video, these electrical signals must be converted into light signals that form the images on the screen. This conversion is done by the display device's components, such as the cathode ray tube (CRT) or liquid crystal display (LCD) backlight. A photodiode, however, is a semiconductor device that converts light into electrical signals, not the other way around. Among the given options, the correct device that converts electrical signals into light signals in the context of television technology is the optical fiber (option A) if referring to signal transmission as light signals, but for direct conversion on the display, none of the options perfectly fit. However, the closest correct answer related to conversion of electrical signals to light signals in display technology is the photo diode (option D) in some contexts like sensors, but not typically in TV displays. The decoder (option C) decodes the signal but does not convert it into light. The transistor (option B) amplifies signals but does not convert them into light. Therefore, the question as posed is somewhat ambiguous, but the best answer among the options for converting signals into light is the photo diode (D), as it is involved in light detection and emission in some devices. The original answer 'C' (Decoder) is incorrect because a decoder processes signals but does not convert them into light signals.

Water freezes from the top surface first because the cold atmosphere cools the surface water, which then forms ice. Ice is less dense than liquid water, so it floats, allowing the water below to remain liquid longer.