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-rwxr-xr-x2102/CH4/EX4.1/exa_4_1.sce14
-rwxr-xr-x2102/CH4/EX4.10/exa_4_10.sce13
-rwxr-xr-x2102/CH4/EX4.11/exa_4_11.sce20
-rwxr-xr-x2102/CH4/EX4.12/exa_4_12.sce18
-rwxr-xr-x2102/CH4/EX4.13/exa_4_13.sce9
-rwxr-xr-x2102/CH4/EX4.14/exa_4_14.sce11
-rwxr-xr-x2102/CH4/EX4.15/exa_4_15.sce12
-rwxr-xr-x2102/CH4/EX4.16/exa_4_16.sce9
-rwxr-xr-x2102/CH4/EX4.17/exa_4_17.sce15
-rwxr-xr-x2102/CH4/EX4.18/exa_4_18.sce13
-rwxr-xr-x2102/CH4/EX4.19/exa_4_19.sce20
-rwxr-xr-x2102/CH4/EX4.2/exa_4_2.sce17
-rwxr-xr-x2102/CH4/EX4.20/exa_4_20.sce14
-rwxr-xr-x2102/CH4/EX4.21/exa_4_21.sce13
-rwxr-xr-x2102/CH4/EX4.22/exa_4_22.sce20
-rwxr-xr-x2102/CH4/EX4.23/exa_4_23.sce11
-rwxr-xr-x2102/CH4/EX4.24/exa_4_24.sce14
-rwxr-xr-x2102/CH4/EX4.25/exa_4_25.sce12
-rwxr-xr-x2102/CH4/EX4.26/exa_4_26.sce14
-rwxr-xr-x2102/CH4/EX4.27/exa_4_27.sce17
-rwxr-xr-x2102/CH4/EX4.28/exa_4_28.sce8
-rwxr-xr-x2102/CH4/EX4.29/exa_4_29.sce11
-rwxr-xr-x2102/CH4/EX4.3/exa_4_3.sce13
-rwxr-xr-x2102/CH4/EX4.4/exa_4_4.sce21
-rwxr-xr-x2102/CH4/EX4.5/exa_4_5.sce11
-rwxr-xr-x2102/CH4/EX4.6/exa_4_6.sce9
-rwxr-xr-x2102/CH4/EX4.7/exa_4_7.sce15
-rwxr-xr-x2102/CH4/EX4.8/exa_4_8.sce23
-rwxr-xr-x2102/CH4/EX4.9/exa_4_9.sce14
29 files changed, 411 insertions, 0 deletions
diff --git a/2102/CH4/EX4.1/exa_4_1.sce b/2102/CH4/EX4.1/exa_4_1.sce
new file mode 100755
index 000000000..a5c681f21
--- /dev/null
+++ b/2102/CH4/EX4.1/exa_4_1.sce
@@ -0,0 +1,14 @@
+// Exa 4.1
+clc;
+clear;
+close;
+// Given data
+Ep= 0.0153*10^-17;//in J
+lamda= 1300;// in nm
+nita_ext= 0.1;
+e = 1.6*10^-19;//in C
+Eg= 1.42*e;// in eV
+S= nita_ext*Eg/e;// in W/A (where S= deltaP/deltaI )
+disp(S,"Slope of efficiency in W/A is : ")
+
+// Note: In the book, the evaluated value of Eg/e is wrong because the value of 1.42*e/e = 1.42 not equal to 0.956 , Hence the answer in the book is wrong
diff --git a/2102/CH4/EX4.10/exa_4_10.sce b/2102/CH4/EX4.10/exa_4_10.sce
new file mode 100755
index 000000000..2e1dfd3f1
--- /dev/null
+++ b/2102/CH4/EX4.10/exa_4_10.sce
@@ -0,0 +1,13 @@
+// Exa 4.10
+clc;
+clear;
+close;
+// Given data
+V_Dmin= 1.5;// in V
+V_Dmax= 2.3;// in V
+Vs= 10;// in V
+R1= 470;// in Ω
+Imax= (Vs-V_Dmin)/R1;// in A
+Imin= (Vs-V_Dmax)/R1;// in A
+disp(Imax*10^3,"The maximum value of current in mA is : ")
+disp(Imin*10^3,"The minimum value of current in mA is : ")
diff --git a/2102/CH4/EX4.11/exa_4_11.sce b/2102/CH4/EX4.11/exa_4_11.sce
new file mode 100755
index 000000000..71cd707df
--- /dev/null
+++ b/2102/CH4/EX4.11/exa_4_11.sce
@@ -0,0 +1,20 @@
+// Exa 4.11
+clc;
+clear;
+close;
+// Given data
+V_Dmin= 1.8;// in V
+V_Dmax= 3;// in V
+// Case first
+Vs= 24;// in V
+R1= 820;// in Ω
+Imin= (Vs-V_Dmax)/R1;// in A
+Imax= (Vs-V_Dmin)/R1;// in A
+disp(Imax*10^3-Imin*10^3,"The variation in current in first case in mA is : ")
+// Case second
+Vs= 5;// in V
+R1= 120;// in Ω
+Imin= (Vs-V_Dmax)/R1;// in A
+Imax= (Vs-V_Dmin)/R1;// in A
+disp(Imax*10^3-Imin*10^3,"The variation in current in first case in mA is : ")
+disp("The variation in current in first case is smaller than in second case, So the brighness in the first case will remain constant , whereas in the second case it will be changing.")
diff --git a/2102/CH4/EX4.12/exa_4_12.sce b/2102/CH4/EX4.12/exa_4_12.sce
new file mode 100755
index 000000000..89e236138
--- /dev/null
+++ b/2102/CH4/EX4.12/exa_4_12.sce
@@ -0,0 +1,18 @@
+// Exa 4.12
+clc;
+clear;
+close;
+// Given data
+Vout= 8;// in V
+V_F= 1.8;// in V
+Ip_max= 16;// in mA
+Ip_max= Ip_max*10^-3;// in A
+I_F= Ip_max;
+Rs1= (Vout-V_F)/I_F;// in Ω
+disp(Rs1,"If V_F= 1.8, then the value of Rs in Ω is :")
+// If
+V_F= 2.0;// in V
+Rs2= (Vout-V_F)/I_F;// in Ω
+disp(Rs2,"If V_F= 2.0, then the value of Rs in Ω is :")
+disp("In either case, the smallest standard value resistor that has a value greater than "+string(Rs1)+ "Ω and "+string(Rs2));
+disp("ohm resistor .is the 390 Ω")
diff --git a/2102/CH4/EX4.13/exa_4_13.sce b/2102/CH4/EX4.13/exa_4_13.sce
new file mode 100755
index 000000000..fb41b0b9b
--- /dev/null
+++ b/2102/CH4/EX4.13/exa_4_13.sce
@@ -0,0 +1,9 @@
+// Exa 4.13
+clc;
+clear;
+close;
+// Given data
+Ip= 1;// in mA
+Pop= 1.5;// in mW
+R= Ip/Pop;// in A/W
+disp(R,"The responsivity of the photodiode in A/W is : ")
diff --git a/2102/CH4/EX4.14/exa_4_14.sce b/2102/CH4/EX4.14/exa_4_14.sce
new file mode 100755
index 000000000..b849b079d
--- /dev/null
+++ b/2102/CH4/EX4.14/exa_4_14.sce
@@ -0,0 +1,11 @@
+// Exa 4.14
+clc;
+clear;
+close;
+// Given data
+lamda= 800;// in nm
+EpIn_eV= 1248/lamda;// in eV
+h_int= 5/100;
+I=50;// in mA
+P= h_int*EpIn_eV*I;// in mW
+disp(P,"Power radiated by an LED in mW is : ")
diff --git a/2102/CH4/EX4.15/exa_4_15.sce b/2102/CH4/EX4.15/exa_4_15.sce
new file mode 100755
index 000000000..7627cbdaf
--- /dev/null
+++ b/2102/CH4/EX4.15/exa_4_15.sce
@@ -0,0 +1,12 @@
+// Exa 4.15
+clc;
+clear;
+close;
+// Given data
+toh_r= 35;// in ns
+toh_nr= 110;// in ns
+toh= toh_r*toh_nr/(toh_r+toh_nr);// in ns
+nita_int= toh/toh_r;
+disp(nita_int,"The internal quantum efficiency is : ")
+
+// Note : There is a calculation error (or miss printed ) in evaluating the value of nita_int (internal quantum efficiency ) so the answer in the book is wrong
diff --git a/2102/CH4/EX4.16/exa_4_16.sce b/2102/CH4/EX4.16/exa_4_16.sce
new file mode 100755
index 000000000..b305e4bfd
--- /dev/null
+++ b/2102/CH4/EX4.16/exa_4_16.sce
@@ -0,0 +1,9 @@
+// Exa 4.16
+clc;
+clear;
+close;
+// Given data
+N1= 6*10^6;// Number of EHPs generated
+N2= 8*10^6;// Number of incident photons
+nita= N1/N2;
+disp(nita*100,"The quantum efficiency of photon detector in % is : ")
diff --git a/2102/CH4/EX4.17/exa_4_17.sce b/2102/CH4/EX4.17/exa_4_17.sce
new file mode 100755
index 000000000..eaa828043
--- /dev/null
+++ b/2102/CH4/EX4.17/exa_4_17.sce
@@ -0,0 +1,15 @@
+// Exa 4.17
+clc;
+clear;
+close;
+// Given data
+e= 1.6*10^-19;// in C
+Eg= 0.75*e;// in J
+h= 6.62*10^-34; // in Js
+c= 3*10^8;// in m/s
+n=90/100;
+// Formula Eg= h*c/lamda
+lamda= h*c/Eg;// in m
+lamda=lamda*10^9;// in nm
+R= n*lamda/1248;// in A/W
+disp(R,"Responsivity in A/W is : ")
diff --git a/2102/CH4/EX4.18/exa_4_18.sce b/2102/CH4/EX4.18/exa_4_18.sce
new file mode 100755
index 000000000..d4f62c0a8
--- /dev/null
+++ b/2102/CH4/EX4.18/exa_4_18.sce
@@ -0,0 +1,13 @@
+// Exa 4.18
+clc;
+clear;
+close;
+// Given data
+V_Dmin= 1;// in V
+V_Dmax= 2;// in V
+Vs= 20;// in V
+R1= 470;// in Ω
+Imax= (Vs-V_Dmin)/R1;// in A
+Imin= (Vs-V_Dmax)/R1;// in A
+disp(Imax*10^3,"The maximum value of current in mA");
+disp(Imin*10^3,"The maximum value of current in mA");
diff --git a/2102/CH4/EX4.19/exa_4_19.sce b/2102/CH4/EX4.19/exa_4_19.sce
new file mode 100755
index 000000000..7fd53600c
--- /dev/null
+++ b/2102/CH4/EX4.19/exa_4_19.sce
@@ -0,0 +1,20 @@
+// Exa 4.19
+clc;
+clear;
+close;
+// Given data
+V_Dmin= 2.5;// in V
+V_Dmax= 5;// in V
+// Case First
+Vs= 25;// in V
+Rs= 250;// in Ω
+Imax= (Vs-V_Dmin)/Rs;// in A
+Imin= (Vs-V_Dmax)/Rs;// in A
+disp(Imax*10^3-Imin*10^3,"The variation in current in first case in mA is : ")
+// Case sec
+Vs= 10;// in V
+Rs= 130;// in Ω
+Imax= (Vs-V_Dmin)/Rs;// in A
+Imin= (Vs-V_Dmax)/Rs;// in A
+disp(Imax*10^3-Imin*10^3,"The variation in current in second case in mA is : ")
+disp("Hence for the 25-V supply, the brightness of LED will be constant and for 10 V , it will be change")
diff --git a/2102/CH4/EX4.2/exa_4_2.sce b/2102/CH4/EX4.2/exa_4_2.sce
new file mode 100755
index 000000000..d9a5399ae
--- /dev/null
+++ b/2102/CH4/EX4.2/exa_4_2.sce
@@ -0,0 +1,17 @@
+// Exa 4.2
+clc;
+clear;
+close;
+// Given data
+e = 1.6*10^-19;//in C
+Eg= 1.48*e;// in J
+R=1;// in Ω
+i_p= 100;// in mA
+i_p= i_p*10^-3;// in A
+i_F= 10;// in mA
+i_F= i_F*10^-3;// in A
+Popt= 1.25;// in mW
+Popt= Popt*10^-3;// in W
+nitaP= Popt/((i_p^2*Eg/e)+i_F^2*R)*100;// in %
+disp(nitaP,"Power efficiency in % is : ")
+
diff --git a/2102/CH4/EX4.20/exa_4_20.sce b/2102/CH4/EX4.20/exa_4_20.sce
new file mode 100755
index 000000000..b4c0ea7a1
--- /dev/null
+++ b/2102/CH4/EX4.20/exa_4_20.sce
@@ -0,0 +1,14 @@
+// Exa 4.20
+clc;
+clear;
+close;
+// Given data
+V1= 0.3;// in V
+V2= 0.7;// in V
+R1= 6;// in kΩ
+R2= 6;// in kΩ
+Vs= 12;// in V
+I1= (Vs-V1)/R1;// in mA
+I2= (Vs-V2)/R2;// in mA
+disp(I1,"The value of I1 in mA is : ")
+disp(I2,"The value of I2 in mA is : ")
diff --git a/2102/CH4/EX4.21/exa_4_21.sce b/2102/CH4/EX4.21/exa_4_21.sce
new file mode 100755
index 000000000..937bff7b7
--- /dev/null
+++ b/2102/CH4/EX4.21/exa_4_21.sce
@@ -0,0 +1,13 @@
+// Exa 4.21
+clc;
+clear;
+close;
+// Given data
+n=40/100;
+lamda= 800;// in nm
+Ip = 2*10^-6;// in A
+R= n*lamda/1248;
+// part (b)
+Pop= Ip/R;// in W
+disp(R,"Responsivity is : ")
+disp(Pop,"The received optical power in watt is : ")
diff --git a/2102/CH4/EX4.22/exa_4_22.sce b/2102/CH4/EX4.22/exa_4_22.sce
new file mode 100755
index 000000000..ef4c48562
--- /dev/null
+++ b/2102/CH4/EX4.22/exa_4_22.sce
@@ -0,0 +1,20 @@
+// Exa 4.22
+clc;
+clear;
+close;
+// Given data
+I=35;// in mA
+I=I*10^-3;// in A
+lamda=1300*10^-9;// in m
+h= 6.62*10^-34; // in Js
+c= 3*10^8;// in m/s
+e= 1.6*10^-19;// in C
+toh_r= 30;// in ns
+toh_nr= 90;// in ns
+toh= toh_r*toh_nr/(toh_r+toh_nr);// in ns
+nita_int= toh/toh_r;
+disp(nita_int,"The internal quantum efficiency is : ")
+Ep= h*c/lamda;// in J
+P= nita_int*Ep*I/e;// in W
+disp(P*10^3,"The optical power generated internally to the LED in mW is : ");
+
diff --git a/2102/CH4/EX4.23/exa_4_23.sce b/2102/CH4/EX4.23/exa_4_23.sce
new file mode 100755
index 000000000..043c7f9a8
--- /dev/null
+++ b/2102/CH4/EX4.23/exa_4_23.sce
@@ -0,0 +1,11 @@
+// Exa 4.23
+clc;
+clear;
+close;
+// Given data
+lamda= 600;// in nm
+h_int= 4/100;
+EpIn_eV= 1248/lamda;// in eV
+I=50;// in mA
+P= h_int*EpIn_eV*I;// in mW
+disp(P,"Power radiated by an LED in mW is : ")
diff --git a/2102/CH4/EX4.24/exa_4_24.sce b/2102/CH4/EX4.24/exa_4_24.sce
new file mode 100755
index 000000000..481d5f946
--- /dev/null
+++ b/2102/CH4/EX4.24/exa_4_24.sce
@@ -0,0 +1,14 @@
+// Exa 4.24
+clc;
+clear;
+close;
+// Given data
+
+V_Dmin= 2;// in V
+V_Dmax= 4;// in V
+Vs= 15;// in V
+R1= 470;// in Ω
+Imax= (Vs-V_Dmin)/R1;// in A
+Imin= (Vs-V_Dmax)/R1;// in A
+disp(Imax*10^3,"The maximum value of current in mA is : ")
+disp(Imin*10^3,"The minimum value of current in mA is : ")
diff --git a/2102/CH4/EX4.25/exa_4_25.sce b/2102/CH4/EX4.25/exa_4_25.sce
new file mode 100755
index 000000000..3684956eb
--- /dev/null
+++ b/2102/CH4/EX4.25/exa_4_25.sce
@@ -0,0 +1,12 @@
+// Exa 4.25
+clc;
+clear;
+close;
+// Given data
+Vout= 10;// in V
+V_F= 2;// in V
+Ip_max= 15;// in mA
+Ip_max= Ip_max*10^-3;// in A
+I_F= Ip_max;
+Rs= (Vout-V_F)/I_F;// in Ω
+disp(Rs,"The value of Rs in Ω is :")
diff --git a/2102/CH4/EX4.26/exa_4_26.sce b/2102/CH4/EX4.26/exa_4_26.sce
new file mode 100755
index 000000000..7868e9619
--- /dev/null
+++ b/2102/CH4/EX4.26/exa_4_26.sce
@@ -0,0 +1,14 @@
+// Exa 4.26
+clc;
+clear;
+close;
+// Given data
+Ep= 0.0153*10^-17;//in J
+lamda= 1300;// in nm
+nita_ext= 0.1;
+e = 1.6*10^-19;//in C
+Eg= 1.42*e;// in eV
+S= nita_ext*Eg/e;// in W/A (where S= deltaP/deltaI )
+disp(S,"Slope of efficiency in W/A is : ")
+
+// Note: In the book, the evaluated value of Eg/e is wrong because the value of 1.42*e/e = 1.42 not equal to 0.956 , Hence the answer in the book is wrong
diff --git a/2102/CH4/EX4.27/exa_4_27.sce b/2102/CH4/EX4.27/exa_4_27.sce
new file mode 100755
index 000000000..fa896d5ad
--- /dev/null
+++ b/2102/CH4/EX4.27/exa_4_27.sce
@@ -0,0 +1,17 @@
+// Exa 4.27
+clc;
+clear;
+close;
+// Given data
+e = 1.6*10^-19;//in C
+Eg= 1.48*e;// in J
+R=1;// in Ω
+i_p= 100;// in mA
+i_p= i_p*10^-3;// in A
+i_F= 10;// in mA
+i_F= i_F*10^-3;// in A
+Popt= 1.25;// in mW
+Popt= Popt*10^-3;// in W
+nitaP= Popt/((i_p^2*Eg/e)+i_F^2*R)*100;// in %
+disp(nitaP,"Power efficiency in % is : ")
+
diff --git a/2102/CH4/EX4.28/exa_4_28.sce b/2102/CH4/EX4.28/exa_4_28.sce
new file mode 100755
index 000000000..b34107f68
--- /dev/null
+++ b/2102/CH4/EX4.28/exa_4_28.sce
@@ -0,0 +1,8 @@
+// Exa 4.28
+clc;
+clear;
+close;
+kT= 0.025;// in eV (Let as take T=300 K)
+E= 1.42/2;// in ev (Let E = E_C-E_F)
+FE= %e^(-E/kT);
+disp(FE,"The probability of exciting electrons at conduction band will be ")
diff --git a/2102/CH4/EX4.29/exa_4_29.sce b/2102/CH4/EX4.29/exa_4_29.sce
new file mode 100755
index 000000000..99f2d3989
--- /dev/null
+++ b/2102/CH4/EX4.29/exa_4_29.sce
@@ -0,0 +1,11 @@
+// Exa 4.29
+clc;
+clear;
+close;
+k= 1.38*10^-23;
+T= 300;// in K (assume)
+V_D= 0.7;// The depletion voltage for silicon
+e=1.6*10^-19;// in C
+// n_n/n_p= p_p/p_n = %e^(e*V_D/(k*T))
+ratio= %e^(e*V_D/(k*T));// ratio of majority to minority charge carriers in n and p of a silicon semiconductor
+disp(ratio,"Ratio of majority to minority charge carriers in n and p of a silicon semiconductor is : ")
diff --git a/2102/CH4/EX4.3/exa_4_3.sce b/2102/CH4/EX4.3/exa_4_3.sce
new file mode 100755
index 000000000..ca357efe8
--- /dev/null
+++ b/2102/CH4/EX4.3/exa_4_3.sce
@@ -0,0 +1,13 @@
+// Exa 4.3
+clc;
+clear;
+close;
+// Given data
+lamda= 670;// in nm
+h_int= 1/100;
+EpIn_eV= 1248/lamda;// in eV
+I=50;// in mA
+P= h_int*EpIn_eV*I;// in mW
+disp(P,"Power radiated by an LED in mW is : ")
+
+// Note : There is a calculation error in evaluating the value of P so the answer in the book is wrong
diff --git a/2102/CH4/EX4.4/exa_4_4.sce b/2102/CH4/EX4.4/exa_4_4.sce
new file mode 100755
index 000000000..5ca4adb36
--- /dev/null
+++ b/2102/CH4/EX4.4/exa_4_4.sce
@@ -0,0 +1,21 @@
+// Exa 4.4
+clc;
+clear;
+close;
+// Given data
+I=40;// in mA
+I=I*10^-3;// in A
+lamda=1310*10^-9;// in m
+h= 6.62*10^-34; // in Js
+c= 3*10^8;// in m/s
+e= 1.6*10^-19;// in C
+toh_r= 30;// in ns
+toh_nr= 100;// in ns
+toh= toh_r*toh_nr/(toh_r+toh_nr);
+nita_int= toh/toh_r;
+disp(nita_int,"The internal quantum efficiency is : ")
+Ep= h*c/lamda;// in J
+P= nita_int*Ep*I/e;// in W
+disp(P*10^3,"The optical power generated internally to the LED in mW is : ");
+
+// Note : There is a calculation error in evaluating the value of P so the answer in the book is wrong
diff --git a/2102/CH4/EX4.5/exa_4_5.sce b/2102/CH4/EX4.5/exa_4_5.sce
new file mode 100755
index 000000000..165e3b30d
--- /dev/null
+++ b/2102/CH4/EX4.5/exa_4_5.sce
@@ -0,0 +1,11 @@
+// Exa 4.5
+clc;
+clear;
+close;
+// Given data
+// Part (a)
+R= 0.85;// in A/W
+Pop= 1;// in mW
+Ip= R*Pop;// in mA
+disp(Ip,"Part (a) The photocurrent in mA is : ")
+disp("Part (b) If the incident light power is 2mW then it is not proportional to Pop so it can not be found the value of photocurrent")
diff --git a/2102/CH4/EX4.6/exa_4_6.sce b/2102/CH4/EX4.6/exa_4_6.sce
new file mode 100755
index 000000000..f9fc0e080
--- /dev/null
+++ b/2102/CH4/EX4.6/exa_4_6.sce
@@ -0,0 +1,9 @@
+// Exa 4.6
+clc;
+clear;
+close;
+// Given data
+N1= 5.4*10^6;// Number of EHPs generated
+N2= 6*10^6;// Number of incident photons
+nita= N1/N2;
+disp(nita*100,"The quantum efficiency at 1300 nm in % is : ")
diff --git a/2102/CH4/EX4.7/exa_4_7.sce b/2102/CH4/EX4.7/exa_4_7.sce
new file mode 100755
index 000000000..07ac1bc0a
--- /dev/null
+++ b/2102/CH4/EX4.7/exa_4_7.sce
@@ -0,0 +1,15 @@
+// Exa 4.7
+clc;
+clear;
+close;
+// Given data
+e= 1.6*10^-19;// in C
+Eg= 0.75*e;// in J
+h= 6.62*10^-34; // in Js
+c= 3*10^8;// in m/s
+n=70/100;
+// Formula Eg= h*c/lamda
+lamda= h*c/Eg;// in m
+lamda=lamda*10^9;// in nm
+R= n*lamda/1248;// in A/W
+disp(R,"Responsivity in A/W is : ")
diff --git a/2102/CH4/EX4.8/exa_4_8.sce b/2102/CH4/EX4.8/exa_4_8.sce
new file mode 100755
index 000000000..e9d796115
--- /dev/null
+++ b/2102/CH4/EX4.8/exa_4_8.sce
@@ -0,0 +1,23 @@
+// Exa 4.8
+clc;
+clear;
+close;
+// Given data
+n=50/100;
+lamda= 900;// in nm
+R= n*lamda/1248;// in A/W
+disp(R,"Responsivity in A/W is : ")
+
+// Part (b)
+Ip= 10^-6;// in A
+Pop= Ip/R;// in W
+disp(Pop,"The received optical power in W is : ")
+
+// Part (c)
+h= 6.62*10^-34; // in Js
+c= 3*10^8;// in m/s
+// Pop= n*h*c/lamda
+n= Pop*lamda*10^-9/(h*c);
+disp(n,"The corresponding number of received photons is : ")
+
+// Note : There is a calculation error in evaluating the value of n (number of received photons) , so the answer in the book is wrong
diff --git a/2102/CH4/EX4.9/exa_4_9.sce b/2102/CH4/EX4.9/exa_4_9.sce
new file mode 100755
index 000000000..1410f9128
--- /dev/null
+++ b/2102/CH4/EX4.9/exa_4_9.sce
@@ -0,0 +1,14 @@
+// Exa 4.9
+clc;
+clear;
+close;
+// Given data
+V=4;// in V
+Vr1= 0.7;// in V
+Vr2= 0.3;// in V
+R1= 4;// in kΩ
+R2= 4;// in kΩ
+I1= (V-Vr1)/R1;// in mA
+I2= (V-Vr2)/R2;// in mA
+disp(I1,"The value of I1 in mA is : ")
+disp(I2,"The value of I2 in mA is : ")