Question

Vsible part of electromagnetic spectrum consists of rodiations having a wavelength in the range of (a) \(400-800 \mathrm{~nm}\) (b) \(300-2600 \mathrm{~nm}\) 1d) \(390-760 \mathrm{~nm}\) (d) \(650-760 \mathrm{~nm}\).

Short answer

The visible part of the electromagnetic spectrum is in the range of 390-760 nm.

Step-by-step solution

Consulting known data

The visible spectrum of the electromagnetic radiation usually ranges from about 380 to 750 nanometers (nm). This is the portion of the electromagnetic spectrum that is visible to (can be detected by) the human eye.

Matching known data with options

Review the given options and find the one that most closely matches the range you know represents the visible spectrum. The range should start at approximately 380 nm and end at or near 750 nm.

Selecting the correct option

Option (c) 390-760 nm is the closest to the actual known range of the visible spectrum and thus is the correct choice. Although option (a) 400-800 nm seems close, it exceeds the upper limit of the typical visible spectrum range.

Key concepts

Electromagnetic Radiation

Electromagnetic radiation is a form of energy that is all around us and takes many forms, such as radio waves, microwaves, X-rays, and gamma rays. Sunlight that we see as white light actually consists of a range of colors, each with its own wavelength. Electromagnetic radiation travels in waves and spans a broad spectrum from very long radio waves to very short gamma rays. The human eye can only detect a very small portion of this spectrum called visible light.

Electromagnetic radiation can be described by its wavelength—the distance between the crests of the waves. This property will determine its color when it comes to visible light and its energy level for all types of electromagnetic radiation. Understanding this concept is crucial for comprehending the various applications and effects of electromagnetic waves, ranging from the use of microwaves to cook food to the potential dangers of exposure to high-energy radiation like gamma rays.

Wavelength

The wavelength of electromagnetic radiation is fundamental to its identity. Specifically, for visible light, the wavelength will determine the color we perceive. The wavelength is measured from peak to peak (or trough to trough) on a wave and is often represented in units of meters, centimeters, or, for the visible spectrum, nanometers (nm), which are a billionth of a meter.

Longer wavelengths correspond to reds at one end of the visible spectrum, and the wavelengths become progressively shorter towards the violet end of the spectrum. In the broader electromagnetic spectrum, visible light represents just a narrow band, with wavelengths longer than visible light including the infrared and radio waves, and shorter wavelengths including ultraviolet light, X-rays, and gamma rays.

Nanometers (nm)

In the context of the electromagnetic spectrum, particularly visible light, the nanometer (nm) is the standard unit of measurement for wavelength. One nanometer equals one billionth of a meter (\(10^{-9}\text{ meters}\)). This incredibly small measurement scale is well-suited to describe the wavelengths of visible light, which range from about 380 nm to 750 nm.

In these terms, when we talk about colors like violet, blue, green, yellow, orange, and red, we're actually referring to light waves that have wavelengths within specific nanometer ranges. That's why scientific instruments that measure light do so with great precision, often down to the nanometer or even smaller, to accurately determine the characteristics of light.

Light Detection by Human Eye

The human eye is sensitive to a very particular range of wavelengths within the electromagnetic spectrum, known as the visible spectrum. This range extends approximately from 380 to 750 nanometers. Within this range, the human eye perceives different wavelengths as different colors, with violet on the low end, and red on the high end of the spectrum.

Within the retina of the eye, there are specialized cells called rods and cones. The rods are more sensitive to light and motion, while the cones are responsible for our color vision. Cones come in three types, each sensitive to a range of wavelengths corresponding to the colors red, green, or blue. This is why color blindness can occur when one or more types of cones are absent or not functioning properly. The ability to see this colorful world is a vital aspect of the human experience, and understanding how our eyes detect light allows us to appreciate our perception and how it is influenced by the physics of light.