Optics Lenses Concave lens Optical Centre Focal length

Optics光學

Lenses透鏡 Concave lens凹透鏡 Optical Centre 光心 Focal length焦距 Principal axis 主軸 2 F’ Focus焦點 2 F A. Optical prosperities of concave lens 凹透鏡的光學特性 1. Parallel lights 平行光 Diverging from focus 由焦點散射 2 F’ F’ F 2 F

Lenses透鏡 Concave lens凹透鏡 2. Towards focus射向焦點 Parallel emerging 平行射出 2 F’ F’ F 2 F 2. Towards focus 射向焦點 Further diverged 進一步散射 2 F’ F’

Lenses透鏡 Concave lens凹透鏡 3. Towards optical centre 射向光心 NOT diverged (no direction change)没有散射 (無改變方向) 2 F’ F’ F 2 F B. Image formation 成像 1. Object is within focal length 實物在焦距以內 2 F’ F’ Nature of image 像的性質 - diminished 縮小 - virtual image 虛像 - erect 正立 F 2 F

Lenses透鏡 Concave lens凹透鏡 B. Image formation 成像 2. Object is between F amd 2 F 實物在F與2 F之間 Light ray 光線 1 2 F’ F’ F Nature of image 像的性質 - diminished 縮小 - virtual image 虛像 - erect 正立 2 F Light ray 光線 2 Discussion 討論 1. How would light ray 1 change as the object moves away? 當實物移離，光線 1 會怎樣改變？ 2. How would light ray 2 change as the object moves away? 當實物移離，光線 2 會怎樣改變？ Conclusion 結論 As object moves away, the image __________. Nature of image : __________, _____. 當實物移離� 像_________________。 像的性質︰______、______。 Classwork 堂課練習 BK 3 p. 182 e. g. 18. 4

Lenses透鏡 Convex lens凸透鏡 Optical Centre 光心 Focal length焦距 Principal axis 主軸 2 F’ Focus焦點 2 F A. Optical prosperities of convexlens 凸透鏡的光學特性 1. Parallel lights 平行光 Converge to focus 向焦點滙聚 2 F’ F’ F 2 F

Lenses透鏡 Convex lens凸透鏡 A. Optical prosperities of concave lens 凹透鏡的光學特性 2. Pass through focus 射穿焦點 Parallel emerge 平行射出 2 F’ F’ F 2 F

Lenses透鏡 Convex lens凸透鏡 A. Optical prosperities of concave lens 凹透鏡的光學特性 3. Pass optical centre 射穿光心 (no direction change) (無改變方向) 2 F’ F’ F 2 F B. Image formation 成像 1. Object is within focal length 實物在焦距以內 Nature of image 像的性質 - enlarged/magnified 放大了 - virtual image 虛像 - erect 正立 Magnifying glass 放大鏡 2 F’ F’ F 2 F

Lenses透鏡 Convex lens凸透鏡 B. Image formation 成像 2. Object is at focus 實物在焦點上 Nature of image 像的性質 - infinitely large 無限大 - virtual image 虛像 - erect 正立 Emerging light rays are parallel 射出的光線互相平行 2 F’ F’ F 3. Object is between F’ and 2 F’ 實物在F’和2 F’之間 2 F’ F’ 2 F Nature of image 像的性質 - enlarged/magnified 放大了 - real image 實像 - inverted 倒置 F 2 F

Lenses透鏡 Convex lens凸透鏡 B. Image formation 成像 4. Object is at 2 F’ 實物在 2 F’上 2 F’ F’ Nature of image 像的性質 - same size as object 與實物大小相同 - real image 實像 - inverted 倒置 F 5. Object is out of 2 F’ 實物在 2 F’以外 2 F’ F’ 2 F Nature of image 像的性質 - diminished 縮小 - real image 實像 - inverted 倒置 F 2 F

Lenses透鏡 Convex lens凸透鏡 B. Image formation 成像 6. Object is at infinity 實物在無限遠 2 F’ F’ Nature of image 像的性質 - diminished 縮小 - real image 實像 - inverted 倒置 F 2 F

Check point p. 188 Q 3 (a) The image is inverted, diminished and real. 像是倒置、縮小的實像。 (b) The image is erect, magnified and virtual. 像是正立，放大的虛像。 (c) The image is erect, diminished and virtual. 像是正立、縮小的虛像。 (d) The image is erect, diminished and virtual. 像是正立、縮小的虛像。

Exercise p. 188 Q 4 (a) (c) (b) (d) Note : arrow to show direction of each section of light 注意︰每段光線必須配以箭嘴以顯示光線的方向

Exercise p. 188 Q 5 The image is erect, magnified and virtual. 像是正立、放大的虛像。

Exercise p. 188 Q 6 The image is erect, diminished and virtual. 像是正立、縮小的虛像。

Exercise p. 188 Q 7 The focal length is 6 × 2 = 12 cm. 焦距 6 × 2 = 12 cm

Exercise p. 188 Q 8 (a)

Exercise p. 188 Q 8 (b) Discussion 討論 Suppose there are 400 light rays emerging from the tip of the object and reach the lens. How many light ray can reach the tip of the image? 設有400條光線由實物的頂端射出並到達透鏡。 有多少條光線能到達像的頂端？ The upper is covered, 上半部被掩蓋 ? How many light ray can reach the tip of the image? ? 有多少條光線能到達像的頂端？

Exercise p. 188 Q 8 further discussion 進階討論 What if the outer part of the lens is covered by a ring? 若鏡的外圍被一個圈掩蓋� 會如何？ What if the centre part of the lens is covered by circular disc? 若鏡的中心被一個圓形碟子掩蓋� 會如何？

Summary on images formed by lenses 透鏡成像總結 V: virtual R: real Concave lens 凹透鏡 M: magnified Image is always erect, diminished, and virtual D: diminished E: erect Convex lens I: inverted Object position 實物位置 Image position 像的位置 Within focal length 在焦距以內 Same side as object 在實物一方 At focus 在焦點 Same side as object, infinity. 在實物一方，無限遠。 Between F and 2 F 在F與2 F之間 Other side, out of 2 F 另一方，2 F以外 At 2 F 在 2 F Out of 2 F 2 F以外 Other side, between F and 2 F 另一方，在F與2 F之間 Very far away 很遠 At F (focus) 在F (焦點) Image properties 像的特性