Understanding Visible Light Wavelengths

The question asks us to identify which colour of light has a wavelength longer than that of yellow light. To answer this, we need to recall the order of colours in the visible light spectrum.

The Visible Light Spectrum and Wavelength Order

Visible light is part of the electromagnetic spectrum. It consists of different colours, each corresponding to a specific range of wavelengths. The colours of the visible spectrum are commonly remembered by the acronym VIBGYOR or ROYGBIV. This sequence also represents the order of wavelengths.

• VIBGYOR: Violet, Indigo, Blue, Green, Yellow, Orange, Red
• ROYGBIV: Red, Orange, Yellow, Green, Blue, Indigo, Violet

The order ROYGBIV lists the colours from the longest wavelength to the shortest wavelength. This means:

• Red light has the longest wavelength.
• Violet light has the shortest wavelength.
• As you move from Red towards Violet in the spectrum, the wavelength decreases.

The approximate wavelength ranges for these colours are:

From this order (ROYGBIV), we can see the sequence is Red > Orange > Yellow > Green > Blue > Indigo > Violet in terms of decreasing wavelength. This means colours appearing earlier in this sequence have longer wavelengths than colours appearing later.

Comparing Wavelengths Relative to Yellow Light

We are given four options: Green, Blue, Orange, and Violet. We need to compare their wavelengths to that of Yellow light.

Looking at the ROYGBIV order:

• R (Red)
• O (Orange)
• Y (Yellow)
• G (Green)
• B (Blue)
• I (Indigo)
• V (Violet)

Yellow is in the middle of this sequence. Colours to the left of Yellow have longer wavelengths, and colours to the right have shorter wavelengths.

• Orange is to the left of Yellow. Therefore, Orange has a longer wavelength than Yellow.
• Green is to the right of Yellow. Therefore, Green has a shorter wavelength than Yellow.
• Blue is to the right of Yellow. Therefore, Blue has a shorter wavelength than Yellow.
• Violet is to the right of Yellow. Therefore, Violet has a shorter wavelength than Yellow.

Conclusion on Light Colour Wavelengths

Based on the order of the visible light spectrum by wavelength (ROYGBIV), Orange light has a wavelength longer than Yellow light. Green, Blue, and Violet light all have wavelengths shorter than Yellow light.

The final answer is the colour with a wavelength longer than Yellow.

Revision Table: Visible Light Wavelengths

Additional Information on Light and Wavelength

Wavelength ($\lambda$) is the distance between successive crests or troughs of a wave. For light, wavelength is inversely proportional to frequency ($\nu$) and directly proportional to the speed of light ($c$), according to the formula $c = \lambda \nu$. This means that light with a longer wavelength has a lower frequency, and light with a shorter wavelength has a higher frequency. The energy of a photon is directly proportional to its frequency ($E = h\nu$), where $h$ is Planck's constant. Therefore, red light (longer wavelength, lower frequency) carries less energy per photon than violet light (shorter wavelength, higher frequency).