Answer:
486nm
Explanation:
in order for an electron to transit from one level to another, the wavelength emitted is given by Rydberg Equation which states that
![\frac{1}{wavelength}=R.[\frac{1}{n_{f}^{2} } -\frac{1}{n_{i}^{2} }] \\n_{f}=2\\n_{i}=4\\R=Rydberg constant =1.097*10^{7}m^{-1}\\subtitiute \\\frac{1}{wavelength}=1.097*10^{7}[\frac{1}{2^{2} } -\frac{1}{4^{2}}]\\\frac{1}{wavelength}= 1.097*10^{7}*0.1875\\\frac{1}{wavelength}= 2.06*10^{6}\\wavelength=4.86*10{-7}m\\wavelength= 486nm\\](https://tex.z-dn.net/?f=%5Cfrac%7B1%7D%7Bwavelength%7D%3DR.%5B%5Cfrac%7B1%7D%7Bn_%7Bf%7D%5E%7B2%7D%20%7D%20-%5Cfrac%7B1%7D%7Bn_%7Bi%7D%5E%7B2%7D%20%7D%5D%20%5C%5Cn_%7Bf%7D%3D2%5C%5Cn_%7Bi%7D%3D4%5C%5CR%3DRydberg%20constant%20%3D1.097%2A10%5E%7B7%7Dm%5E%7B-1%7D%5C%5Csubtitiute%20%5C%5C%5Cfrac%7B1%7D%7Bwavelength%7D%3D1.097%2A10%5E%7B7%7D%5B%5Cfrac%7B1%7D%7B2%5E%7B2%7D%20%7D%20-%5Cfrac%7B1%7D%7B4%5E%7B2%7D%7D%5D%5C%5C%5Cfrac%7B1%7D%7Bwavelength%7D%3D%201.097%2A10%5E%7B7%7D%2A0.1875%5C%5C%5Cfrac%7B1%7D%7Bwavelength%7D%3D%202.06%2A10%5E%7B6%7D%5C%5Cwavelength%3D4.86%2A10%7B-7%7Dm%5C%5Cwavelength%3D%20486nm%5C%5C)
Hence the photon must possess a wavelength of 486nm in order to send the electron to the n=4 state
The railroad tracks will expand because the heat waves make them bigger
Answer:
The plane would need to travel at least 
(
.)
The 
runway should be sufficient.
Explanation:
Convert unit of the the take-off velocity of this plane to 
:
.
Initial velocity of the plane: 
.
Take-off velocity of the plane 
.
Let 
denote the distance that the plane travelled along the runway. Since acceleration is constant but unknown, make use of the SUVAT equation 
.
Notice that this equation does not require the value of acceleration. Rather, this equation make use of the fact that the distance travelled (under constant acceleration) is equal to duration 
times average velocity 
.
The distance that the plane need to cover would be:
.
Answer:
Dynamic flexibility
Explanation:
Dynamic flexibility can be generally defined as the ability of the body muscles and joints to move in full range of motion. High flexibility in these joints and muscles leads to the decreasing pain and injury in different parts of the body.
Proper warm up exercises are needed to be carried out that involves both the combination of controlling movements and stretching of the body, and this directly enhances the dynamic flexibility of the body.
The athletes and sports persons possesses a good dynamic flexibility of their body as they carry our different types of body exercises.
