標題:
F4 physics wave 與 光學
發問:
當光線以大於臨界角穿過一樣物件，就會發生total internal reflection，咁反射的角度係咩？ 例如有一樣物件的臨界角是 45度 當光以 （45+1）度，即是46度穿過，反射角是 （90-1）度，即是89度，定是直接由90度跳去 46度？ 仲有，光由低密度的medium 去高密度的medium，例如空氣去水，會唔會有臨界角的概念？如果有的又係點？ 幫幫忙！ please~
最佳解答:
Q:當光線以大於臨界角穿過一樣物件，就會發生total internal reflection，咁反射的角度係咩？ A: When total internal reflection (全內反射) occurs, the Law of Reflection holds. That said, the angle of incident (入射角) equals to the angle of reflection (出射角). Q: 例如有一樣物件的臨界角是 45度. 當光以 （45+1）度，即是46度穿過，反射角是 （90-1）度，即是89度，定是直接由90度跳去 46度？ A: When the incident angle is 46 degrees, which is larger than the critical angle (臨界角), the Law of Reflection holds. Therefore, the reflected angle is 46 degrees (NOT 89 degrees). On reaching the critical angle, the refracted ray (折射線) will disappear suddenly and the reflected ray will appear. Q: 光由低密度的medium 去高密度的medium，例如空氣去水，會唔會有臨界角的概念？如果有的又係點？ A: Total internal reflection will not occur when light travels from a less dense medium to a denser medium. From Snell's Law, sin(i)/sin(r) = n where i and r are the incident and reflected angles respectively n is the refractive index of a medium Hence, sin(r) = sin(i)/n When light travels from air to water, for example, the greatest value for i = 90 degrees. Then, sin(r) = sin(90)/n = 1/n < 1 because n for water is greater than one. You would still have a real refracted angle. Hence, total internal reflection doesn't happen. 2014-07-13 21:02:18 補充： sorry...a typo in the sentence under Snell's Law, it should read: where i and r are the incident and REFRACTED angles respectively
其他解答:
臨界角就是折射角等於90度，即是折射光沿界面走，不會穿越界面，當入射角大於臨界角，折射光會被界面反射，就如鏡面一樣，這就是total internal reflection，單鏡機就是用三菱鏡反射光線，一些望遠鏡亦用一對菱鏡縮短鏡管長度。光由空氣入水同樣有臨界角，但對你沒意義，在水中你的影像才有意義，但大於臨界角對你更有意義，因為你可見到你的反影，如俗語說，沒有水，撒泡尿也可見到自己樣子如何。
F4 physics wave 與 光學
發問:
當光線以大於臨界角穿過一樣物件，就會發生total internal reflection，咁反射的角度係咩？ 例如有一樣物件的臨界角是 45度 當光以 （45+1）度，即是46度穿過，反射角是 （90-1）度，即是89度，定是直接由90度跳去 46度？ 仲有，光由低密度的medium 去高密度的medium，例如空氣去水，會唔會有臨界角的概念？如果有的又係點？ 幫幫忙！ please~
最佳解答:
Q:當光線以大於臨界角穿過一樣物件，就會發生total internal reflection，咁反射的角度係咩？ A: When total internal reflection (全內反射) occurs, the Law of Reflection holds. That said, the angle of incident (入射角) equals to the angle of reflection (出射角). Q: 例如有一樣物件的臨界角是 45度. 當光以 （45+1）度，即是46度穿過，反射角是 （90-1）度，即是89度，定是直接由90度跳去 46度？ A: When the incident angle is 46 degrees, which is larger than the critical angle (臨界角), the Law of Reflection holds. Therefore, the reflected angle is 46 degrees (NOT 89 degrees). On reaching the critical angle, the refracted ray (折射線) will disappear suddenly and the reflected ray will appear. Q: 光由低密度的medium 去高密度的medium，例如空氣去水，會唔會有臨界角的概念？如果有的又係點？ A: Total internal reflection will not occur when light travels from a less dense medium to a denser medium. From Snell's Law, sin(i)/sin(r) = n where i and r are the incident and reflected angles respectively n is the refractive index of a medium Hence, sin(r) = sin(i)/n When light travels from air to water, for example, the greatest value for i = 90 degrees. Then, sin(r) = sin(90)/n = 1/n < 1 because n for water is greater than one. You would still have a real refracted angle. Hence, total internal reflection doesn't happen. 2014-07-13 21:02:18 補充： sorry...a typo in the sentence under Snell's Law, it should read: where i and r are the incident and REFRACTED angles respectively
其他解答:
臨界角就是折射角等於90度，即是折射光沿界面走，不會穿越界面，當入射角大於臨界角，折射光會被界面反射，就如鏡面一樣，這就是total internal reflection，單鏡機就是用三菱鏡反射光線，一些望遠鏡亦用一對菱鏡縮短鏡管長度。光由空氣入水同樣有臨界角，但對你沒意義，在水中你的影像才有意義，但大於臨界角對你更有意義，因為你可見到你的反影，如俗語說，沒有水，撒泡尿也可見到自己樣子如何。
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