How Does White Light Affect The Strength Of Red Light
Light that is visible to the human eye is a small portion of the electromagnetic spectrum which can vary in colour based on the wavelength of what is being seen at any particular time. This visible light has a primary function of causing electrons to become more active with higher energy rates. The colour that is seen revolves around the size of this portion which is noted as the wavelength. White light is a culmination of all colours which is the cause of it being the brightest. Furthermore, when the wavelength is larger, the energy that is being directed is spread out across a larger distance which explains why red light (700 nanometres) is often less visible then a blue or violet light (400nm).
Light when travelling in the electromagnetic spectrum in a void always has a constant speed of 3x108 m/s. When this passes through a solid or liquid which consists of a …show more content…
density, the light is likely to either diffract, refract or a combination of both. This solid or liquid which it can pass through is called the ‘medium’ which light travels through. Diffraction as defined by the University of Tennessee. is a result where when light hits an object or collides with a barrier, it has the capability to ‘bend’ past the obstacle losing some of the light wave but having a majority of the wave continue travelling past.
While diffraction can influence light as it travels, this report was investigating refraction and how it influences the dispersion of the various colours of the visible light spectrum. Refraction occurs when light moves between two mediums which have a different density. This change in density causes the direction of light propagation to bend either towards or away from the normal. Dispersion is a result that occurs when various colours are transitioned simultaneously into a new medium causing the various wavelengths to react differently and each have a unique amount of refraction. Most commonly this is investigated with white light which Hyperphysics (2016) states is comprised of all colours.
The minimum amount of deviation is a value which can be calculated when a light passes through a prism symmetrically. This symmetrical positioning of the light likely brings the deviation to a minimum as the various distances travelled and different angles of incidence cannot influence the deviation. Holyoke college brings evidence that the minimum deviation can be used to determine the refractive index (n) which is a ratio comparing lights velocity in comparison to any other medium. This index can then be used in various equations to investigate how light interacts with the transition. This refractive index has been investigated by Hyperphysics who reported that it is able to be modelled against the inverse of the wavelength to bring a linear model which can be transformed into a generalized model for any prism to form n = a + b/λ2. The a and b values are constants which vary for each individual prism. Not only can this refractive index be modelled to form a linear line but it can also be used to investigate the dispersive power of a specific prism with the use of the formula ω=(n_b-n_r)/(n_y-1) where ω = dispersive power and the other values . Each individual prism will have its own unique dispersive power for comparison with the medium and we’ll see how its fine travels through. (Dr Jan W Gooch, 2007)
Experimental Discussion:
The refractive index must be a property of the glass as in, the two media that are used in the dispersion as it has been stated that refraction is a ratio based on the difference in density as light travels from one medium to the other.
Furthermore, the refractive index is used to calculate the change in the angle at the point of transition while having no influence over the distance travelled inside the prism. Due to this, it supports the previous statement as if it does not affect distance travelled, the shape of the prism should not matter.
Amrita states that the standardised value for the dispersive power of a glass prism should lie between 0.04 and 0.05. The results obtained while conducting this experiment do lie within this expected value when taking into consideration the uncertainty calculated for the dispersive power. There are numerous reasons why the dispersive power could be almost out of the range of the standardised value including but not limited to a measurement error or there may have been impurities in the glass prism that was throughout the trial
period.
These impurities in the glass prism can be categorised as a systematic instrumental error in which it cannot be corrected within the timeframe provided for experimentation. While this is the most likely cause of the variation from the generally accepted mean, it could also but due to random uncontrollable errors or blunders in areas such as reading the scale and lining up the crosshair. To attempt to minimise the risk of these random errors two people always worked in tandem to line up the crosshair while two read the scale.
Should this experiment be repeated in the future, it would be advisable to use three identical triangular prisms too allow the values of dispersion to be averaged and compared to achieve a significantly more accurate result. Secondly, another method that would optimise accuracy would be to repeat the trial using a different apex to make a comparison of the minimum deviation at the three differ points.
Investigations of this nature have a variety of applications centred around current technology as well as modernizing scientific processes. The way light travels and how it disperses is a required knowledge when looking into technology such as projectors and the recently popular RGB (red-green-blue) lights which require an efficient use of white light. One example of a scientific application of knowledge specifically centred on dispersion power is when a prism is being utilized for a spectrum analysis to determine information such as the chemical composition of a substance. These are but a few of the current uses of this information and the variety and importance of these numbers is likely to increase as light is investigated in greater depth.
Conclusion:
The aim of this experiment was to investigate a glass triangular prism and how it causes a white light to disperse its colours. This aim was thoroughly investigated as not only was the dispersive power calculated but also the refractive index of this specific prism. The results very closely aligned to the expected relationships as when the graph was plotted, a linear graph was formed that matched the expected values when taking into account the measurement limitations. Overall the measurements and the methods in which they were taken appear to be scientifically sound with a minimized amount of systematic error due to control over many possible errors.
Light when travelling in the electromagnetic spectrum in a void always has a constant speed of 3x108 m/s. When this passes through a solid or liquid which consists of a …show more content…
density, the light is likely to either diffract, refract or a combination of both. This solid or liquid which it can pass through is called the ‘medium’ which light travels through. Diffraction as defined by the University of Tennessee. is a result where when light hits an object or collides with a barrier, it has the capability to ‘bend’ past the obstacle losing some of the light wave but having a majority of the wave continue travelling past.
While diffraction can influence light as it travels, this report was investigating refraction and how it influences the dispersion of the various colours of the visible light spectrum. Refraction occurs when light moves between two mediums which have a different density. This change in density causes the direction of light propagation to bend either towards or away from the normal. Dispersion is a result that occurs when various colours are transitioned simultaneously into a new medium causing the various wavelengths to react differently and each have a unique amount of refraction. Most commonly this is investigated with white light which Hyperphysics (2016) states is comprised of all colours.
The minimum amount of deviation is a value which can be calculated when a light passes through a prism symmetrically. This symmetrical positioning of the light likely brings the deviation to a minimum as the various distances travelled and different angles of incidence cannot influence the deviation. Holyoke college brings evidence that the minimum deviation can be used to determine the refractive index (n) which is a ratio comparing lights velocity in comparison to any other medium. This index can then be used in various equations to investigate how light interacts with the transition. This refractive index has been investigated by Hyperphysics who reported that it is able to be modelled against the inverse of the wavelength to bring a linear model which can be transformed into a generalized model for any prism to form n = a + b/λ2. The a and b values are constants which vary for each individual prism. Not only can this refractive index be modelled to form a linear line but it can also be used to investigate the dispersive power of a specific prism with the use of the formula ω=(n_b-n_r)/(n_y-1) where ω = dispersive power and the other values . Each individual prism will have its own unique dispersive power for comparison with the medium and we’ll see how its fine travels through. (Dr Jan W Gooch, 2007)
Experimental Discussion:
The refractive index must be a property of the glass as in, the two media that are used in the dispersion as it has been stated that refraction is a ratio based on the difference in density as light travels from one medium to the other.
Furthermore, the refractive index is used to calculate the change in the angle at the point of transition while having no influence over the distance travelled inside the prism. Due to this, it supports the previous statement as if it does not affect distance travelled, the shape of the prism should not matter.
Amrita states that the standardised value for the dispersive power of a glass prism should lie between 0.04 and 0.05. The results obtained while conducting this experiment do lie within this expected value when taking into consideration the uncertainty calculated for the dispersive power. There are numerous reasons why the dispersive power could be almost out of the range of the standardised value including but not limited to a measurement error or there may have been impurities in the glass prism that was throughout the trial
period.
These impurities in the glass prism can be categorised as a systematic instrumental error in which it cannot be corrected within the timeframe provided for experimentation. While this is the most likely cause of the variation from the generally accepted mean, it could also but due to random uncontrollable errors or blunders in areas such as reading the scale and lining up the crosshair. To attempt to minimise the risk of these random errors two people always worked in tandem to line up the crosshair while two read the scale.
Should this experiment be repeated in the future, it would be advisable to use three identical triangular prisms too allow the values of dispersion to be averaged and compared to achieve a significantly more accurate result. Secondly, another method that would optimise accuracy would be to repeat the trial using a different apex to make a comparison of the minimum deviation at the three differ points.
Investigations of this nature have a variety of applications centred around current technology as well as modernizing scientific processes. The way light travels and how it disperses is a required knowledge when looking into technology such as projectors and the recently popular RGB (red-green-blue) lights which require an efficient use of white light. One example of a scientific application of knowledge specifically centred on dispersion power is when a prism is being utilized for a spectrum analysis to determine information such as the chemical composition of a substance. These are but a few of the current uses of this information and the variety and importance of these numbers is likely to increase as light is investigated in greater depth.
Conclusion:
The aim of this experiment was to investigate a glass triangular prism and how it causes a white light to disperse its colours. This aim was thoroughly investigated as not only was the dispersive power calculated but also the refractive index of this specific prism. The results very closely aligned to the expected relationships as when the graph was plotted, a linear graph was formed that matched the expected values when taking into account the measurement limitations. Overall the measurements and the methods in which they were taken appear to be scientifically sound with a minimized amount of systematic error due to control over many possible errors.